474 BOTANICAL GAZETTE [December 



GERMINATION OF THE ZOOSPORE 



. The duration of the motile condition of the zoospores varies; 

 some ceased to be motile within 10 minutes, while others were still 

 moving after more than 90 minutes; but in any case, when the 

 zoospore becomes sluggish, the body gradually becomes spherical 

 and the cilia are withdrawn or become coalescent with the plasma 

 membrane. 



About two hours after the quiescence of the zoospore, the 

 outermost layer of the plasma membrane becomes changed into a 

 delicate cell wall. The nucleus at this time is in the resting condi- 

 tion, with a centrosome-like structure and radiations near the 



membrane 



remains 



during the next 20 hours (fig. 204). The presence of centrosome- 

 like structures and radiations is not a definite feature; at about 24 

 hours after quiescence they may (figs. 206, 207) or may not be 

 visible (figs. 205, 208). 



The first segmentation division of the germinating zoospore 



* 



takes place 24 hours after its quiescence. The nucleus enters 

 prophase either at the center of the cell (fig. 209) or in its elongated 

 part (fig. 210), and when the chromosomes are arranged at the 

 equatorial plate (figs. 211, 213), two centrosome-like structures 



The polar view of the metaphase shows 

 distinctly 24 chromosomes (figs. 212, 214). Each of the chromo- 

 somes divides longitudinally and half of each passes to each pole 

 (fig- 2I S)- The second mitosis in these two nuclei 

 succession (figs. 21 7-2 21) or simultaneously (fig. 222 



are present at the poles. 



may 



A 



__ „ prophase and 



view of metaphase. 



In the zoosporelings consisting of three cells the three nuclei 

 divide in various order (figs. 224, 225), and in prophase of any 

 nucleus 24 chromosomes are present. In the further nuclear 

 divisions in the development of the zoosporelings the same number 

 of chromosomes is counted. This young sporeling after a multitude 

 of cell divisions (figs. 226-228) develops into a long filamentous 

 structure instead of a stout column. The product at about the 

 end of 20 days after germination is shown in fisr. r*. a. In habit 



>j 



filamentous 



