Illustrated Guide to Trees and Shrubs: A Handbook of the Woody Plants of the Northeastern United States and Adjacent Canada/Revised Editionby Arthur Harmount Graves
Authoritative, easily accessible guide omits lengthy technical descriptions in favor of easy-to-use keys covering such characteristics as leaves, twigs, bark, buds, seeds, stems, fruit or fruit stalks, and other identifying traits. Over 300 pen-and-ink drawings by Maud H. Purdy, noted botanical illustrator. "I recommend this book most highly." — Farida A. Wiley,… See more details below
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Authoritative, easily accessible guide omits lengthy technical descriptions in favor of easy-to-use keys covering such characteristics as leaves, twigs, bark, buds, seeds, stems, fruit or fruit stalks, and other identifying traits. Over 300 pen-and-ink drawings by Maud H. Purdy, noted botanical illustrator. "I recommend this book most highly." — Farida A. Wiley, American Museum of Natural History.
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Illustrated Guide to Trees and Shrubs
A Handbook of the Woody Plants of the Northeastern United States and Adjacent
By Arthur Harmount Graves
Dover Publications, Inc.Copyright © 1984 Elizabeth Graves Brigham
All rights reserved.
Nomenclature. For plant names I have followed Gray's Manual, eighth edition, for the most part, but have used also Rehder's Manual, and Standardized Plant Names, second edition, 1942. The last was prepared by a special committee in 1923 for the purpose of unifying or standardizing the names of the higher plants important in horticulture. This is certainly a laudable object, for the many names for some of our plants have led to much confusion. But this is a big country: even the area covered by this book is about half again as large as that of the British Isles. And so there will be of necessity many common names, or at least more than one, for our common plants, and on this account I have often cited more than one. What we should strive for, however, is to have a uniform single scientific or botanical name. This should serve to identify any given plant with certainty. I have always given the preferred common name first.
Trees, shrubs, and vines. What dimensions must a woody plant have to entitle it to be classed as a tree? Formerly Sudworth included woody plants having one well-defined stem and a more or less definitely formed crown and attaining a height of at least 8 feet and a diameter of not less than 2 inches. Harlow and Harrar (26, p. 1) have extended the height to 20 feet. Blakeslee and Jarvis (5, p. 434) say 15 feet. I should be inclined to accept the last figure, but the whole matter is of course entirely arbitrary. Shrubs, i. e. woody plants with many more or less erect stems, such as the Lilac, often reach a height of much more than 8 feet, but can not therefore be classed in the category of trees. Japanese potted trees (Brooklyn Botanic Garden Guide no. 6, 1931) have been dwarfed by special methods and are only a few feet in height, but are nevertheless properly called trees. (See also P. & G. 5: no. 3. 1949. and 6: 68–79. 1950.) It would seem that for admission to the class of trees, the habit or form of the plant is of as much importance as the ultimate height.
Vines are either herbaceous or woody, and in the latter case may also be called climbing shrubs. They twine around or fasten themselves to other plants or suitable supports or they trail along the ground. Such are the Grape, Virginia Creeper, Clematis, Poison-ivy etc. They are known technically as lianas and are much more abundant in tropical forests.
Classification. For the order of families I have used the "natural" system of Engler which is familiar to all botanists. In general, this system depends upon the evolutionary rank of each family — the oldest first and the most recently evolved families last. Thus the Gymnosperms, an ancient group, precede the Angiosperms, which are more modern; and in the Angiosperms the families follow each other in a sequence depending upon their supposed relative ages, with the Compositae, the most modern family of all, at the end.
For the uninitiated, a few words may be in order here about the terms genus, species, etc. The genus is the larger group, as for example; Birch, Betula. The species are the kinds of birch as Betula lenta, Sweet Birch, B. papyrifera, Paper B., etc. Species may be further divided into varieties. Nearly related genera, as Betula, the Birch, Carpinus, the Hornbeam, and Ostrya, the Hop-hornbeam, all are classed together in the same family, which in this case is the Birch Family, Betulaceae. Nearly related families are grouped together to form orders: as, for example, in the case of the Beech Family, Fagaceae, which, with the related Betulaceae, belongs to the order Fagales. In this book I have omitted the orders, since they are not essential to our purpose. Orders again are grouped into classes, and so on to the main divisions of the plant kingdom from the most ancient to the most modern, as follows:
Division 1. Thallophytes. Bacteria, Algae, Fungi, Lichens.
Division 2. Bryophytes. Mosses and Hepatics.
Division 3. Pteridophytes. Including Clubmosses, Horsetails and True Ferns.
Division 4. Spermatophytes. Seed Plants.
Gymnosperms. (Gymnos — naked and spermon — seed). Woody plants in which the seeds are borne naked on the surface of cone scales. This group includes the Cycads, mostly now tropical or subtropical plants.
Angiosperms. (Angion — vessel and spermon — seed). Flowering plants. Either woody or herbaceous; seeds enclosed in an ovary (angion) as in Orange, Locust, Blueberry etc.
Monocotyledons. Flowering plants with only one cotyledon (seed-leaf) in the embryo. Includes grasses, lilies, irises, orchids, palms, etc.
Dicotyledons. Flowering plants with 2 cotyledons in the embryo. Highest group of flowering plants, some herbaceous and some woody. Most of the plants in this book belong to this group and to the Gymnosperms.
Although some of the earliest botanists centuries ago divided all plants into two classes, namely, herbs and woody plants, it is obvious that the woody plants are not a "natural" group from a systematic viewpoint. In some families, as in the Maple Family, all members are woody; in others, as in the Heath Family, some are woody, some herbaceous. In general, however, the large plants of our time are woody. If we make the acquaintance of these, the herbaceous members may soon fall into their proper places.
Woody Plant Characters. During the growing season, woody plants can of course be most readily identified by their leaves. Also important are the characters of the branchlets with their buds, and the bark of the older branches and of the trunk. Flowers and fruits are also very helpful, and sometimes practically necessary; but their absence at certain times of the year and on young specimens makes them less desirable as key characters.
The features of a winter twig are less familiar to most people than those of a leafy stem. For this reason a brief description of a typical winter twig, such as that of the Bigtooth Aspen, is given here. At the tip of the stem is a large bud, the terminal bud, A, Fig. 1. Along the sides of the stem are other buds, lateral buds, cf. B, usually smaller, each one situated above a leaf scar, C. A leaf scar is the mark left where a leaf of the previous summer fell from the stem. The location of buds above the leaf scars shows that these buds were formed in the axils of the leaves; and they are, therefore, called axillary buds. Some plants do not have a true terminal bud: in such cases the leaf scar is of course immediately below the "false" terminal bud; and on the other side of the twig we find a short stub or scar indicating the dead end of the season's growth. (Cf. Fig. 103, p. 213.) The leaf scar is marked with several small dots; these are the vascular bundle scars, cf. D, marking the places where the conducting strands ("veins") extended from the stem into the leaf. On this stem there is a pair of small scars, one on each side of the leaf scar; these are stipule scars, cf. E, showing where these appendages were attached. (Many plants do not have stipules.) The place on the stem where a leaf is borne (in some plants several leaves) is called a node, F, and the part of the stem between two adjacent nodes is the internode, G. Scattered over the surface of the stem are small dotlike markings, slightly raised. These are the lenticels, H, regions of loosely fitting cells with air spaces among them, in the otherwise impervious corky covering of the stem.
A bud is an undeveloped shoot; it consists of a little stem, bearing tiny leaves, or flowers, or both; in woody plants of this climate it usually has its lowest leaves modified into scales, bud scales, I, which cover and protect the rest of the bud. The arrangement of the bud scales also differs: in the majority of plants they overlap each other, shingle fashion, and are then called imbricate; or they may touch each other only at their edges, two or three of them covering the whole bud in this way, an arrangement called valvate; or, rarely, only a single cap-like scale may cover the whole bud.
The young stem and leaves within the bud lie dormant during the winter. In the spring the stem begins to lengthen and the leaves to expand, and the scales drop off. By this unfolding of the terminal bud, the stem that bears it becomes longer. The internodes between the expanding foliage leaves usually lengthen considerably, but those between the bud scales lengthen very little or not at all. Hence, when the bud scales fall, they leave a series of scars very close together; the scars themselves are very narrow, and they look like a succession of rings around the stem. A group of such bud scale scars, J, marks the beginning of each year's growth in length; these are visible on the stem for a number of years, until they are obliterated by its growth in thickness. The age of a twig can be determined by counting the groups of bud scale scars back from the tip. Some of the axillary buds may develop similarly, forming side branchlets, cf. N.
But some plants have naked buds; i. e., buds without typical scales. In these plants the outermost, leaflike parts of the bud are nevertheless protective and often drop off with the unfolding of the bud.
Most woody plants have buds of definite growth, in which all the leaves that are to develop on a given branchlet in one season are laid down in the bud the previous summer. When these leaves have expanded, the stem stops growing in length, and usually forms a terminal bud, unless the branchlet ends in a flower or flower cluster; a bud is also formed in the axil of each of the leaves. But some plants have buds of indefinite growth, in which there are a few fully formed leaves, and many others just beginning. When such a bud unfolds, the fully formed leaves expand and some of the partly formed leaves finish their development, and buds are formed in their axils. Such a stem continues to grow in length and to put out new leaves until cold weather stops it in the fall; it forms no terminal bud, and its growth in length the next year is taken up usually by the uppermost well-formed axillary bud.
The stem interior is divided roughly into three concentric regions; bark, K, wood, L, and pith, M. The age of any part of the stem may be determined by counting the annual rings in the wood, which are clearly visible in cross section. The age thus determined would, of course, agree with the age computed by counting groups of bud scale scars.
The phyllotaxy, or arrangement of leaves on the stem (and consequently the arrangement of axillary buds), is in a general way constant for each species, although there may be some variation on different parts of the same plant, and occasionally some distortion due to twisting of the stem during growth. In identifying a plant by its leaves or buds, it is of the utmost importance first of all to observe its phyllotaxy. The leaves may be arranged in whorls (circles) of three or more at a node (Pl. XLI, 2 and 3, p. 226), or they may be opposite each other on the stem (2 at a node, see Pl. XXVIII, p. 171). In these cases we must consult the key to opposite or whorled leaves or buds. More often, however, leaves, or rather their points of insertion on the stem, are in a spiral arrangement, that is, an imaginary line connecting these points of insertion will be a spiral (Fig. 1a). Then the phyllotaxy is expressed by the distance around the cylindrical stem from one leaf to the next. Thus, if the next leaf of the spiral is halfway around the stem the phyllotaxy is called ½, and the third leaf will be directly above the first, as in Fig. 34, p. 112. More commonly the distance around the stem from one leaf to the next is equal to 2/5 of the stem circumference, and we must pass through five leaves and twice around the stem before arriving at the leaf directly above the one at the starting point. This is 2/5 phyllotaxy (e. g., Pl. XXIV, 1, p. 162 and Fig. 71, p. 155). It will be seen that the denominator of this fraction shows the number of leaves passed before we arrive at the one directly above the starting point, and the numerator the number of turns around the stem. In the bayberry the phyllotaxy is 3/8, and successively higher fractions occur in pine cones, sunflower fruit heads, etc. Thus we can always ascertain what the next higher phyllotaxy would be by adding the numerators and denominators of the two preceding phyllotaxies; ½, 1/3, 2/5, 3/8, 5/13, etc. These relations are obviously the result of geometrical space requirements of the dividing cells at the growing point of the stem where the leaves originate.
Excerpted from Illustrated Guide to Trees and Shrubs by Arthur Harmount Graves. Copyright © 1984 Elizabeth Graves Brigham. Excerpted by permission of Dover Publications, Inc..
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