File:Bulletin (Pennsylvania Department of Forestry), no. 11 (1901) (20314740959).jpg

Title: Bulletin (Pennsylvania Department of Forestry), no. 11
Identifier: bulletinpennsylv11penx (find matches)
Year: 1901 (1900s)
Authors: Pennsylvania. Dept. of Forestry
Subjects: Forests and forestry
Publisher: Harrisburg, Pa. : The Department : WM. Stanley Ray, state printer of Pennsylvania
Contributing Library: Penn State University
Digitizing Sponsor: Lyrasis Members and Sloan Foundation

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i PLATE III. TYPES OF BUDS. 1. 3.' 4. 5. ti. Sugar Maple (ojntosite). Chfstnut (alteruate). Butternut (superjiosed). 1J«'(1 Maple (at'cessorv). Striped Maple (stalkVd). Striped Maple (valvate). Kod Oak (scaly). Ruttonwood (sub-petiolar). lieecli (solitary tcnninal). Black Oak (elustcr.Ml and liairv terminal). Basswood (axillary and pseudo-terniinal). Anu^rican Elm sliowiuK (1) leaf buds and (f) flower buds. 13. Papaw (naked flower- and leaf-buds). 14. Ominion Locust (imbedded). !•>. Trembling Aspen (siiarjt-ijointed). Drawing.s are about one-half natural size. s. 'J. 10. 11. 11', 87 often hairy. As they develop during the season they become firmer and often lose their green color and their hairs. The direction of the new growth is variable. In many species it takes at first a drooping direction and later, as its elements become firmer, it as- sumes a horizontal or ascending position. The new growth of the Pines is conspicuous in that it grows in an erect direction at first and later becomes horizontal or drooping. The taste, smell, and color of the twigs are helpful in distinguish- ing some of our common species. The twigs of some species as the Black Birch, Spice Bush, Sassafras, and Wild Cherry have a char- acteristic taste and smell. The color of the twigs may be green as in the Sassafras, red as in the Basswood and Red Maple, or brown as in the Sugar Maple. Many other different colors and combina- tions of color aid materially in distinguishing our trees. Some twigs are rough while others are rather smooth. They may be roughened by hairs, lenticels, raised leaf-scars, bud-scale scars, warty or resinous exudations, corky projections, or decurrent projections of the bark. If we examine a young twig just after it has emerged from the bud we will find that it is usually green in color. At the end of the first season's growth a thick bark has usually developed which is no longer green on the surface, but, by cutting a cross section of a twig, one will often find that the inner bark is still green. This green tissue develops chlorophyll and manu- factures food just as does the green tissue of the leaves. As the bark increases in thickness the chlorophyll decreases, eventually dis- appearing entirely from the stem. In order that this green tissue in the bark may function it is necessary that gases be exchanged through the bark. Special structural modifications on the bark known as lenticels (Figs. 96 and 98) make possible this exchange of gases just as the stomata on the leaf-surfaces allow and even regu- late the exchange of the gases of the leaf. The lenticels are very numerous and conspicuous on some species, while on others they are rare and inconspicuous. They are raised on some species like the Elder, while on others they are even with the bark. Their color varies. They may be wiiite, gray, pinkish, yel- low, brown, or black. In outline they are usually circular or slightly elongated. In the Cherries and Birches they are confluent, a char- acteristic which results in the horizontally elongated lines of lenti- cels (Figs. 96 and 98) so common on their trunks. The duration of the lenticels varies with the species and its en- vironment. As a rule the more rapidly bark is formed the shorter is the duration of the lenticels. On some species it is diflScult to find lenticels on any but the last season's growth while on others they may persist for some years. The exfoliation of the bark causes their 1

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