178 



ECOLOGY 



forest floor, try to establish it, noting especially tl^eir relation 

 to the relative moisture of the soil and to light. 

 References. Clements, 59 ; Principles, Chapter XXXVII ; 

 Warming-Graebner, 57 ; Schimper-Fisher, 56. 



Fig. 6. Model for grouping of drawings in type studies 



A, base of a plant of shepherd's purse (Capsella bursorpastoris) , x J; r, the main 

 root ; B, upper part of the inflorescence, XI; G, two leaves, — I from the 

 upper part ; II from the base of the plant, XI; D, a flower, x 3 ; E, the 

 same, with sepals and petals removed, X S; F, petal ; G, sepal ; H, stamen, 

 X 10; /, filament; an., anther; I, a fruit with one of the valves removed to 

 show the seeds, x 4; j, longitudinal section of a seed, X S; K, the embryo 

 removed from the seed, X 8 ; ^, the first leaves (cotyledons) ; St., the stem end- 

 ing in the root; L, cross section of the stem, X 20; fb., fibro-vascular bundle ; 

 M, a similar section of the main root, x 15 ; iV, diagram of the flower. — After 

 Campbell 



160. Field study of zonation. 



A. Select any locality where two or more plant formations 



meet and determine : 



1. The characteristic plants of eacb fprmation. 



