CHYTRIDIALES 101 



Nuclear behavior in Nowakowskie/la ramosa differs from that in 

 Cladochytrium replication, Endochytrium operculatum, and Catenochy- 

 tridium laterale, described earlier, in that there is no appreciable in- 

 crease in nuclear size before division and there are repeated divisions 

 during enlargement of the incipient sporangium both before and after 

 the formation of the sporangial cross wall. Furthermore, although 

 nuclear division in a single sporangium is simultaneous, it is not 

 absolutely synchronous. 



The formation of the resting spore from the pseudoparenchyma is 

 a striking characteristic of Nowakowskiella ramosa. The process was 

 followed cytologically by J. Roberts. Nucleated cells of the pseudoparen- 

 chyma produce short cla T *ate projections. The tips of these become 

 filled with granular cytoplasm as they enlarge. After becoming some- 

 what spherical, the nucleus from the pseudoparenchyma cell migrates into 

 the incipient resting spore, which is then cut oft' by a cross wall. The 

 now centrally disposed nucleus is surrounded by a loosely packed mass 

 of granules from which radiate strands to the periphery. The evenly 

 dispersed oil droplets of the contents finally coalesce into about eight 

 globules. A similar subsequent coalescence of the granules takes place. 

 The cytoplasm itself remains reticulate. After the internal structure of 

 the resting spore becomes stabilized, a striated, thickened inner wall 

 is laid down beneath the original one. No further stages were observed 

 of the mature resting spore. 



The development and nuclear history of INowakowskiella profusa, 

 the other species of the genus investigated by Roberts, offers few sig- 

 nificant variations from that of N. ramosa, save that in it no pseudo- 

 parenchyma or resting spores were formed. 



In the polycentric inoperculate Polychytrium aggregation (p. 478), 

 a strongly chitinophilic form, Ajello (1948a) was able to follow the. 

 nuclear behavior clearly (Fig. 9). His findings revealed that the zoo- 

 spore possesses a conspicuous nuclear cap closely affixed to the nucleus. 

 This structure is formed by the coalescence of granular particles which 

 lie in the immediate vicinity of the nucleus but which could not be 

 definitely identified as mitochondrial in origin. The nucleus of the en- 

 cysted zoospore (Fig. 9 A, p. 102) is spherical or slightly oval, averages 

 3.2 \i in diameter, and contains a deeply staining nucleolus and a 



