198 MORPHOLOGY AND LIFE HISTORY 



middle (X 4); the pistil (X 4); an imagined 

 cross-section of the pistil (X 4). 

 (2) A ground-plan of the flower, 5 cm. in diameter, 

 first drawing five equidistant concentric cir- 

 cles, and filling in the plan as directed by the 

 instructor. 

 (3) An imaginary longitudinal section of the flower 



(X2). 



5. Compare the length of the stamens with that of 

 the pistil. Carefully consider and state the rela- 

 tive probabilities of self-pollination and cross- 

 pollination. 



/. Non-sexual Reproduction: 



i. Non-sexual reproduction in Trillium is confined to 

 the growth of the persistent, underground rhizome. 

 This organ is thick and fleshy, serving for the 

 storage of food. 



K. Sexual Reproduction: 



1. Microspores. 



(a) Mount in clearing fluid (or water) on a slide 

 some of the pollen from an anther. 



(b) Observe (first under low, then under high power) 

 the individual pollen-grains. Describe their 

 color and shape, and note the network of 

 ridges on the surface of each. 



(c) By carefully focusing on individual grains there 

 may readily be detected in some of them one 

 nucleus, in others, two. Those in the one- 

 nucleate stage are mature microspores. 



2. Male gametophyte. The division of the microspore- 

 nucleus is the first stage in the germination of the 

 spore. To what do microspores, when they ger- 



