i8o 



CHARACE/E 



centre, through which the antherozoids force their way, and finally enter 

 the apical cell by the deliquescence of the upper portion of its cell-wall, 

 and coalesce with the apical papilla. The whole contents of the apical 

 cell may be regarded as the oosphere. 



Impregnation causes at first very little external change in the structure 

 of the female organ. The protoplasm of the oosphere, now invested 

 with a cell-wall and transformed into an oosperm^ gives place to starchy 

 or oily matter ; the walls of the enveloping tubes which lie next it in- 

 crease in thickness and hardness, and the oosperm thus becomes invested 

 in a hard black shell or pericarp. The structure thus formed, the so- 

 called ' fruit ' or sper??wcarp of the Characeae ultimately becomes de- 

 tached, falls into the mud at the bottom of the water, and there germinates 

 in the next spring. 



When the spermocarp germinates, the oosperm first divides inta 



Fig. 167. — Calcareous 

 spermocarp of C. 

 hispida (magnified). 



Fig. 166. — A-D, stages in development of archegone o{ K.Jlexilis. b, apex 

 of fertile leaf; x, ' Wendungszellen ; ' K, crown (x 300). (After Sachs.) 



three cells, a large basal and two apical cells, the former apparently 

 serving the purpose of supplying with nutriment the young plant which 

 proceeds from the latter ; and these three cells may be said together to 

 constitute the embryo. From one of the two apical cells proceeds a long 

 hyaline unseptated filament, commonly called the primary root, by means 

 of which the young plant is attached to the soil. The other of the two 

 apical cells develops into a hypha-like filament, consisting at first of a 

 single row of cells with limited apical growth, and called by some writers 

 the 'pro-embryo,' or more correctly \\\q prothalliiun. In this prothallium 

 are developed two primary 7iodes at considerable distance from one 

 another, and separated by a very long internode. From the lower of 

 these two primary nodes there springs a whorl of rhizoids, which soon 



