10 



THE PHYCOMYCETES 



In Polyphagiis euglenae, frequent on Euglena that forms a 

 green film on puddles in pigsties and corrals, a conjugation tube 

 is formed between the uninucleate gametangia. A swelling ap- 



FiG. 19. Physoder77ia zeae-maydis, causing brown spot on com. A. Mature 

 resting sporangium, surface view, with circumscissile lid from which zoo- 

 spores escape, as in B. C. Amoeboid zoospores provided with a single 

 flagellum. D. Rhizomycelium within epidermis of com. E. Segmentation 

 of rhizomycelium to form thick-walled resting sporangia. 



pears on the conjugation tube, into which the protoplasts mi- 

 grate. A spiny, thick-walled zygote, which remains dormant 

 for a few months, results. On o-ermination a tube is formed; 

 into it the two nuclei misstate and fuse; nuclear diyision follows; 

 and many swarm cells are set free to repeat the developmental 

 cycle. 



