Trees of New York State 27 



SPECIAL MORPHOLOGY 



The use of a tree manual entails an nnderstandinp; of the 

 morphology of plant i)arts and of their proper interpretation. 

 The primary basis of classification in trees, as in other seed 

 plants, is the flower, for trees bear flowers as do other plants 

 which produce seed. But the floral stage of trees is a fleeting 

 one at best; floral characters are not available for study except 

 for comparatively short periods. In a taxonomic study of woody 

 l)lants, other specific characteristics such as leaf, twig, fruit and 

 bark are generally stressed at the expense of floral characters. 

 The following pages are devoted to Special Morphology in an 

 endeavor to render more lucid that part of the text which follows : 



General LEAVES 



The expanded green structures which make up the foliage of 

 the higher plants, and in which physiological processes necessary 

 to the life of the plant take place, are known as leaves. Fore- 

 most among such life activities are (1) photosynthesis or the 

 synthesis of sugar from carbon dioxide and water, (2) transpira- 

 tion or the voiding of excess water that has been taken up 

 through root absorption, and (3) respiration or breathing. 



A foliage leaf always possesses an expanded part or lamina 

 which is specially adapted by internal structure and the presence 

 of breathing pores or stomata to perform the functions assigned 

 to it by nature. In addition there may be a stalk or petiole which 

 attaches the lamina to the stem, and stipules, inserted separately 

 on the stem at the base of and on either side of the petiole 

 (Fig. 1). A leaf which is devoid of petiole is said to be epetiolate 



LAM/n/A 



Fig. 1 — Portion of a Twig with Leaf Attached, Showing Leaf Parts 



