CHAPTER X. 



STUDIES OF SELECTED SPERMATOPHYTES. 



In Chapter VIII general directions are given for the 

 study of flowers. The studies which follow are intended 

 to show how in a course of limited time certain plants may 

 be selected to bring out facts of particular interest regard- 

 ing the structure, behavior, and relationship of plants. In 

 this work Kerner and Oliver's " Natural History of Plants " 

 and Miiller's " Fertilization of Flowers " are most useful 

 books of reference. 



Naias flexilis. — Slender Naias. 



This plant flowers in summer, and material should be 

 gathered then and kept in formalin for class use. 



The flowers are of special interest on account of their 

 great simplicity. There are no devices to secure pollina- 

 tion by means of insects, for the plant is entirely submerged, 

 and rooted, and pollen is carried to the stigmas by water 

 currents. In this genus the flowers are monoecious or 

 dioecious. The staminate flower consists of a single sta- 

 men terminating the floral axis, surrounded by a hyaline 

 membrane, and this in turn by a tubular leaf, both of 

 which constitute a double perianth. The pistillate flower 

 consists of a single ovule having the two ovular coats 

 ordinarily found, and an enveloping leaf which may be 

 considered as a carpel. 



Draw staminate and pistillate flowers as seen under a 

 hand lens. 



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