8 



EXPLANATION OF TERMS 



A node is the place of attachment of a leaf or group of leaves. 

 An internode is the portion of a stem cornprised between two 

 nodes. 



Stems and their branches may be erect, or they may be ascend- 

 ing, i. e., rising somewhat obliquely or curving upward. Prostrate 

 stems may emit roots from their joints, when they are said to be 

 creeping, as in the Strawberry. 



The Leaves. 



Leaves are lateral expansions and usually bear a bud in the 

 axil, i. e., the angle formed by the leaf and the stem or branch. 

 They are essentially digestive organs, their function being to com- 

 bine materials brought by the crude sap from the roots with car- 

 bon dioxide obtained from the air, thus forming substances which 

 may be used in building plant tissues. Only green leaves are able 

 to perform this work. 



l 2 



Leaves and Their Arrangement. — 1. Simple leaf; b, blade; p, petiole; 

 s, stipule. 2. Stem with alternate leaves. 3. Stem with opposite, sessile 

 leaves. 4. A whorl of six leaves. 



%*^S 



Compound Leaves. — 1. A palmately compound leaf with three leaflets, as 

 in clovers. 2. A palmately compound leaf with more than three leaflets, as 

 in the Lupine. 3. A pinnately compound leaf with three leaflets, as in Bur 

 Clover and some Hosackias (note the stalk of the terminal leaflet). 4. A pin- 

 nately compound leaf with more than three leaflets, as in the Loco-weed and 

 in some Hosackias. 5. A compound leaf ending in a tendril, as in the 

 Vetches and in the Sweet Pea. 



