Variety of species. 
Number of species. 
4th, red color as a means of increasing temperature? 
red color as a screen to protect from light? 
Function of foliage leaves,—five-fold,— 
1. Carbon-dioxide assimilation, or photosynthesis. 
2) lranspination: 
3. Synthesis of other organic compounds. 
4. Respiration. 
5. Assimilation. 
Parts of the leaf. 
1. Blade or lamina. 
2.) Stalk or petiole: 
3. Stipules, elm, magnolia, etc. 
4. Sometimes hairs, scales, etc. 
Note sessile leaves. 
Simple leaves. 
1. Form of leaf usually constant for given species. 
2. Outline of leaf, ovate, oval, elliptical, lanceolate, linear, 
needle-like, etc. fie 7 
Advantage of simple leaf—amount of surface to light. 
4. Disadvantage of simple leaf when large. 
(i), Casts deeper shade. 
(2) Does not admit as free circulation of air. 
(3) More apt to become injured. 
Venation of leaves,—two types,— 
I. Parallel veined, usually mionocotyledonous plants. - 
Corn, Smilacina, Solomon’s seal. 
2. Netted veined, usually dicotyledonous plants. 
Elm, rose,maple, hawthorn, oak. 
Gu) ealntatics 
(2). Pinnate. 
Cut or lobed leaves, some maples, oaks, birches, poison ivy, 
thistles, dandelion. 
Divided or compound leaves, rose, sumac, e-der, hickory, wal- 
nut, locust, pea, clover, American creeper. 
Significance of forms. 
1. Reduction of surface allows 
(1) Freer movement of air. 
SS 
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