THE STUDY OF LEAVES 19 



there is some tree popularly called red cedar and in all 

 sections some cultivated plant called arborvitas. If a 

 specimen of either of these is taken, the growing twigs 

 will be found covered with scale-like parts and no such 

 things as would usually be called leaves. Each of these 

 scales, because it marks a joint, is a full leaf of the 

 plant (Plate I, Fig. A). 



There is a shrub or small tree, extensively cultivated 

 especially in the East, which has abundant small pink 

 flowers in spring or summer. This will appear to the 

 novice as without show of leaves, seeming to consist 

 of hundreds of green thread-like growths. The name 

 given to the plant is tamarix or tamarisk. If the reader 

 can procure a piece of this plant, let him examine the fine 

 sprays of green thread-like portions with a magnifier. 

 Along these he will observe pointed, triangular, partially 

 clasping parts. These, though smaller than a pinhead, 

 are the simple leaves of this plant. They are full leaves 

 because they are at the joints of the stem (Figs. 35-37). 



The three plants here given, red cedar, arborvitse, and 

 tamarix, have the smallest leaves found on any of our 

 trees and shrubs. 



Large leaves, the largest there are on any of the northern 

 shrubs, will be found on a very beautiful thorny plant called 

 Hercules' club (Fig. 336). These are closely crowded 

 at the blunt ends of the stems. These leaves with their 

 enlarged bases nearly cover the whole surface of the blunt 

 tip. Lower down on the old stem the scars, where the 

 leaves were in earlier years, will show as broad V-shaped 

 marks. The leaves on this plant will often be over a yard 

 long and consist of 75 to 150 blades. 



Arrangement of Leaves. — In this search for leaves mark- 

 ing the joints of stems, one will have noticed that there 

 are frequently two or more leaves at the same joint. Over 

 half of the kinds of cultivated shrubs in the United States 

 have only one leaf at the joint (Plate III, Fig. M) ; a 

 smaller number have two (Plate II, Fig. K) opposite 



