434 PRACTICAL BOTANY 



plasm), which lines the cell-wall, while darker, more 

 granular protoplasm (endoplasm), including the 

 chlorophyll corpuscles, collects towards the centre. 



2. The rupture of the cell-wall by an irregular slit 

 near to the extreme apex of the filament : before the 

 rupture the septum may be seen to present a convex 

 surface to the rest of the filament, indicating greater 

 internal tension in the " zoosporangium " : on rupture 

 this is relieved, and the septum then projects convexly 

 into the cavity of the empty zoosporangium. 



3. The passage of the protoplasmic mass through the 

 opening, by a streaming movement, assisted by more 

 or less marked, screw-like rotation of the whole 

 body: the protoplasm may undergo division at the 

 time of escape, and two zoogonidia may thus be formed. 



4. The rapid movement of the large zoogonidium 

 when free, which may be followed with the naked 

 eye, and under the microscope is seen to be rotatory. 

 The motile period lasts but a short time, and varies in 

 different species. 



Treat a zoogonidium, which has just escaped and is 

 in rapid motion, with a solution of iodine : put on a 

 cover-slip, and examine under a high power : no cell- 

 wall will be visible, though the solution will in some 

 measure plasmolyse the cell. Turning more especially 

 to the ectoplasm, there will be seen numerous cilia, 

 arranged in pairs, projecting from the surface of the 

 zoogonidium, while in the transparent ectoplasm will 

 be seen numerous highly refractive bodies, which stain 

 with iodine : these are nuclei, and a careful observa- 

 tion will show that their position is exactly opposite 

 the insertion of the pairs of cilia. 



