776 AQUATIC PHYCOMYCETES 



outside the infected parts the former seems the more likely. The Plas- 

 modia retain their individuality within the host and their nuclei multiply 

 by protomitosis which is characterized by the formation of cruciform 

 figures, and so forth. Each Plasmodium then becomes transformed into 

 a sorus (sometimes hollow) composed of somewhat spherical sporangia. 

 Certain of the peripheral sporangia may each produce an exit tube, or 

 two may combine to form a single one (Fig. 58 L). Akaryote stages in 

 mitoses precede zoospore formation. Cleavage furrows divide the con- 

 tents of each sporangium into ten or more elongate zoospores. 

 Each spore contains several granules, a refractive elongate body, and 

 a short anterior and long posterior flagellum. Sporangia in the interior 

 of the sorus evidently connect by means of a system of intercommunicat- 

 ing pores with those more peripherally located, and their zoospores are 

 eventually liberated through the latter's discharge tubes. 



In older cultures cystosori are produced. They arise from plasmodia 

 that appear darker than those which yield zoosporangial sori and 

 usually occupy a more central position in the gall. Cleavage lines divide 

 the dark Plasmodium into polygonal blocks which thereupon subdivide 

 into angular thick-walled golden-brown resting spores. These are loosely 

 associated in a spherical or cylindrical group — the cystosorus. No ger- 

 mination of the resting spores was observed. 



KEY TO THE SPECIES OF WORONINA 



Parasitic in aquatic Phycomycetes ; resting spores in compact masses 

 or separate 

 Parasitic in members of the Saprolegniaceae 



Cystosorus composed of globular compact masses of angular 



resting spores W. polycystis, p. 776 



Cystosorus composed of linear groups of unconnected spiny rest- 

 ing spores W. asterina, p. 779 



Parasitic in Pythium W. pythii, p. 781 



Parasitic in fresh-water algae; the resting spores separate, in linear 



groups W. glomerata, p. 779 



WORONINA POLYCYSTIS ConiU 



Ann. Sci. Nat. Bot., V, 15: 176, pi. 7. 1872 

 (Fig. 58 A-C, p. 778) 

 Sporangia sorus terminal or intercalary in segments (often swollen) 



