50 ' BRITISH CHAEOPHTTA. 



side, the remainder of the cell being filled with free 

 protoplasm (Pig. 20 i). The protoplasm contracts 

 slightly, leaving a space between it and the cell- wall, 

 the nucleus on the side nearest to the cell- wall extends 

 in both directions and two very long cilia are produced 

 (Fig. 20 ii). The nucleus gradually narrows and 

 elongates until it forms a very long body coiling 

 about three times round the interior of the cell (Fig. 

 20 iii, iv) and the free protoplasm becomes absorbed. 

 When fully developed the antherozoids burst from 

 their cells and swim about freely in the water 

 (Fig. 20 v). 



Early stages in the development of the antheridium 

 will be seen in Fig. 18. Strasburger is of opinion 

 that the male organ should not be regarded as a single 

 antheridium since he considers that it " contains 

 eight groups of endogenously-formed antheridia," and 

 "should on this account be termed an antheridiophore " 

 (' Text-book,' 4th Engl, ed., p. 423). 



The original cell which goes to form the 

 oogonium first divides horizontally into 

 two cells (Fig. 21 i), the lower being the node-cell, 

 the upper, the oosphere. 



From the periphery of the node-cell portions are 

 cut off forming smaller cells (Fig. 21 ii), which are 

 invariably five in number, elongate upwards, and 

 surround and envelop the oospore. These enveloping 

 cells are contiguoiis and in the earlier stages of 

 growth consist of single cylindrical cells nearly 

 straight and erect (Fig. 21 iii). Before long how- 

 ever a horizontal septum appears dividing each 

 enveloping cell into two (Fig. 21 iv). The lower 

 of these elongates and as growth proceeds assumes a 

 spiral direction, ascending always from right to left. 



