216 NITELLA LESS. 



cells (hd 1 ) are attached, and each of these latter bears four 

 delicate coiled filaments (sp.f.) divided by septa into small 

 cells arranged end to end, and thus not unlike the hyphae of 

 a fungus. There are therefore nearly two hundred of these 

 spermatic filaments in each spermary, coiled up in its interior 

 like a tangled mass of white cotton. 



The cells of which the filaments are composed have at 

 first the ordinary character, but as the spermary arrives at 

 maturity there is produced in each a single sperm (c), having 

 the form of a spirally-coiled thread, thicker at one end than 

 the other, and bearing at its thin end two long flagella. In 

 all probability the sperm proper, i.e., the spirally-coiled body, 

 is formed from the nucleus of the cell, the flagella from its 

 protoplasm. As each of the 200 spermatic filaments con- 

 sists of from 100 to 200 cells, a single spermary gives rise 

 to between 20,000 and 40,000 sperms. 



When the sperms are formed the shields separate 

 from one another and the spermatic filaments protrude 

 between them like cotton from a pod : the sperms then 

 escape from the containing cells and swim freely in the 

 water. 



The ovary (Fig. 45, G, ovy, and Fig. 48 A) is ovoidal in 

 form, attached to the leaf by a short stalk (stk], and ter- 

 minated distally by a little chimney-like elevation or crown 

 (cr). It is marked externally by spiral grooves which can be 

 traced into the crown, and in young specimens its interior is 

 readily seen to be occupied by a large opaque mass (ov}. 

 Sections show that this central body is the ovum, a large cell 

 very rich in starch : it is connected with the unicellular stalk 

 by a small cell (nd} from which spring five spirally-arranged 

 cells (sp. c.) : these coil round the ovum and their free ends 

 each divided by septa into two small cells project at the 

 distal end of the organ and form the crown, enclosing a 



