HYPHOCHYTRIALES 759 



zoospores and a broad apical papilla; rhizoids extremely delicate, much 

 branched; zoospores irregularly ovoid, 2.5-3 u, in diameter, with a large 

 colorless globule, the broader, anterior end bearing a long flagellum, 

 escaping individually through a wide apical pore, movement evenly 

 swimming, not hopping; resting spore broadly lenticular, 30-50 u, in 

 diameter, outer wall thick, colorless, smooth, radially striated, giving a 

 cellulose reaction, inner wall thin, homogeneous, contents with an 

 extremely large globule that nearly fills the lumen, rhizoids delicate, 

 much branched, germination not observed. 



In oogonia of Voucher ia sessilis, V. terrestris, Germany. 



De Wildeman (1895a: 63) described ovoid resting spores with striated 

 walls found in oogonia of Vaucheria sessilis from Belgium and Switzer- 

 land as belonging to this species. Since the sporangia were not observed, 

 however, it is equally possible that these organisms belong to Rhizophy- 

 dium decipiens. Scherffel( 1926a: 221) claims that the resting spores of 

 the two species, which in all other respects are identical (no rhizoids, 

 however, have been observed as yet in R. decipiens), may be distinguish- 

 ed by the fact that in Latrostium comprimens there is a giant globule 

 in the contents, whereas in R. decipiens there are numerous small ones. 

 The validity of this fine distinction can only be determined after both 

 forms have been thoroughly investigated. Resting spores of both types 

 have been found in the same oogonium in Vaucheria terrestris in 

 Michigan. 



HYPHOCHYTRIACEAE 



Thallus eucarpic, polycentric, consisting of relatively broad, branched 

 hyphae with occasional cross walls; sporangia inoperculate, terminal 

 or intercalary; zoospores partly or fully formed within the sporangium 

 or cleaved out at the orifice of the discharge tube; resting spore thick- 

 walled. 



On algae, higher fungi, and vegetable debris. 



It may be practicable in the future to segregate Hyphochytrium caten- 

 oides Karling from that genus, since its zoospores typically are cleaved 

 out after discharge of the contents from the sporangium, and not 

 endogenously produced. 



See remarks under the species, p. 762. 



