LAGENIDIALES 983 



single discharge tube, at least the tip of which is extramatrical; zoo- 

 spores reniform, broadly fusiform or grape-seed-like, laterally biflagel- 

 late, fully formed in the sporangium or in an evanescent vesicle at the 

 orifice of the discharge tube, or cleaved out within the sporangium and 

 completing their development naked or in a more or less quickly eva- 

 nescent vesicle, or, rarely (the primary spores?), moving within the spo- 

 rangium and encysting at the orifice, movement after discharge gen- 

 erally an even swimming, rarely hopping; plants monoecious or 

 dioecious, the gametangia shaped like the sporangia or the female 

 often more rotund, monandrous, in rare instances lacking an anther- 

 idium, the male gametangium forming a fertilization tube, periplasm 

 apparently lacking; oospore borne singly and loosely (except in one 

 species) in the female gametangium, with a thick wall, more or less 

 coarsely granular parietal plasma, a large oil globule, and often a lateral 

 bright spot, germination not (?) observed ; in some species one or more 

 resting spores (apogamous?) formed in a thallus or thallus segment. 

 Parasitic in fresh-water algae, particularly in the vegetative filaments, 

 gametangia, and zygotes of the Conjugatae, in pollen grains; on eggs 

 and newly hatched young of the blue crab (Callinectes); in mosquito 

 larvae, copepods, Daphne, and rotifer eggs. Some species have been 

 cultivated on artificial media. One is saprophytic on human skin. 



One-celled thalli which are transformed at maturity into either zoo- 

 sporangia or gametangia are occasionally developed by the multicel- 

 lular species (for example, Lagenidium rabenhorstii, L. humanum). Some 

 species, however, are typically one-celled (Fig. 80, p. 987). It is a ques- 

 tion whether these should be retained in Lagenidium or segregated in a 

 distinct genus. 1 



In almost half the species of Lagenidium the zoospores are developed 

 more or less completely within the sporangium, as in Olpidiopsis; in the 

 remainder the process takes place exogenously, with or without a sur- 

 rounding vesicle. Although the primary zoospores had been thought to 

 be completely suppressed as in Pythium, Scherffel (1925a) and Karling 



1 Since no zoospores have been reported in Lagenidiopsis, that imperfectly known 

 genus, erected by de Wildeman to include a one-celled dioecious fungus found only 

 in the sexual stage, will not serve the purpose. Karling (1942e) has made the genus 

 synonymous with Lagenidium. 



