A LONG-STALKED ELODEA FLOWEE 47 



While the habits of these two flowers are biological equivalents, 

 and the parts concerned outwardly similar, they are morpholog- 

 ically unlike and in no sense homologous. The "tubus calicis" 

 of the pistillate flower includes that complex of parts above the 

 ovary of the epigynous flower, while that of the staminate flower 

 is simply the stem or axis. The greater efficiency of the latter is 

 probably due to its stem character and the relative simplicity of 

 stem elongation compared with flower elongation. 



The rapid elongation of the peduncle of the staminate flower 

 is due to the lengthening of cells previously much contracted. 

 These cells may increase to twenty-five times their former length, 

 — this accompanied by a slight decrease in diameter. Some stalks 

 elongated over 20 cm. on plants left over night in a collecting 

 case, — the flowers being pushed out through the tangle of plants 

 in the vasculum. 



The flower maturing naturally in the water has usually, during 

 the hours of sunshine at least, a bubble tugging at its apex. 

 Frequent experiment failed, however, to dislodge a bubble in 

 such a way as to carry any of the pollen to the surface. It seems 

 that the pollen is shed only when the flower itself reaches the 

 surface of the water. 



In quiet waters the flowers may remain attached to the plant 

 for some time after the pollen is shed. But in more open waters 

 their release is hastened by wave action, the axis breaking at its 

 most slender part within the spathe at the base. In 1909, when 

 the plants were noted most abundantly, the detached staminate 

 flowers formed extensive windrows at the margins of open water 

 where thousands of them might be seen tangled together by their 

 long trailing stalks. In no case was an unopen flower noted 

 among these and they were free from all except floating pollen. 



Biologically it is of interest to note the occurrence of the three 

 possible flower-forms within the one genus, and the association 

 of two distinct types of staminate flowers with a pistillate flower 

 that is quite constant throughout the genus. While the pistillate 

 flower might also have developed an elongated scape, as in Vallis- 

 neria, the vegetative habits of the plant have not made this neces- 

 sary. Elodea plants are small leaved and thrive near the surface 

 of the water, — a habit that is favored through its anchorage by 

 means of long roots. Vallisneria, on the other hand, has long 

 leaves arising from a short stem at the bottom of the pond, and 



