42 



THE SIMPLE HOLOCARl'IC BIFLAGELLATE PHYCOMYCETES 



obviously impossible to determine which of the para- 

 sites described in the older literature relate to 0. 

 Saprolegn'tae. 



Olpidiopsis Saprolegn'tae Cornu is the type spe- 

 cies of the genus and probably the parasite which 

 Pringsheim mistook for a developmental stage of 

 Saprolegnia. Cornu limited the name 0. Sapro- 

 legn'tae to Saprolegnia — inhabiting parasites the 

 resting spores of which are covered with numerous 

 fine spines, but Fischer ('92) included Cornu's spe- 

 cies in Pseudolpiditim and restricted the name 0. 

 Saprolegn'tae to a species with hemispherical or 

 blunt, hyaline, up to 3 /^ high, warts or pegs on the 

 resting spores. Barrett interpreted 0. Saprolegn'tae 

 in the original sense of Cornu and created a new spe- 

 cies, 0. vexans, for the parasite with warty resting 

 spores described by Fischer. Diehl and Shanor sup- 

 ported Barrett's interpretation, but Coker and Graff 

 accepted Fischer's distinction. The present writer is 

 following Barrett's interpretation of 0. Saproleg- 

 n'tae to a certain degree but only temporarily until 

 all species have been more critically studied. Olpi- 

 diopsis Saprolegn'tae Fischer and 0. vexans Barrett 

 are accordingly reduced to synonyms of 0. incras- 

 sata. However, this does not completely solve the 

 taxonomic problems involved nor greatly aid begin- 

 ners in recognizing and distinguishing Olpidiopsis 

 species. In the first place, 0. incrassata, for instance, 

 is supposedly characterized by resting spores with a 

 wavy undulating exospore, and the introduction un- 

 der this name of synonymous species, 0. Saproleg- 

 n'tae Fischer and 6. vexans, with warty or knobby 

 resting spores destroys this distinction. On the other 

 hand, MeLarty ('41) has clearly shown that 0. Ach- 

 li/ae also may form resting spores with a wavy un- 

 dulating exospore (figs. 58, 61, 66), which obviously 

 indicates that this character is not specific for 0. in- 

 crassata alone. Furthermore, 0. Saprolegn'tae Cornu, 

 according to Shanor ('10), is limited to the same 

 Saprolegnia and Isoachltja hosts as 0. incrassata, 

 with the exception of /. eccentrica. Therefore, on 

 the basis of host relationship there is no distinction 

 between these two species. In view of the fact that 

 sporangium size and shape, number and length of 

 exit tubes, and the character of the exospore no 

 longer appear to be constant for a species, and in 

 the event that Shanor's host range results are con- 

 firmed, it may perhaps be taxonomically expedient 

 to lump all reported Saprolegnia parasites, with the 

 possible exception of O. irregularis, under the name 

 of O. Saprolegn'tae Cornu. In that event, Cornu's 

 species would have the following synonomy: 

 Chytridium Saprolegniae Braun, I.e. 

 Olpidium Saprolegniae Braun, I.e. 

 Olpidiopsis incrassata Cornu, I.e., p. 146. 

 O. Saprolegniae Fischer, I.e. 

 O. major Maurizio, 1895. Jaliresber. Nat. Ges. Griiu- 



bundens 38: 15. 

 O. echinata Petersen, I.e. 

 O. oexans Barrett, 1913. Ann. Bot. -2i>: -231. 

 Diplophysa Saprolegniae Schroder, I.e. 

 Pseudolpiditim Saprolegniae Fischer, I.e. 

 P, incrassatum Fischer, I.e. 



Such a classification is based entirely on host re- 

 lationship, which is often a questionable criterion of 

 distinction. Nevertheless, the author is inclined to 

 agree at present with Petersen's view that 0. Sapro- 

 legniae and 0. incrassata may possibly be identical. 

 The results of Shanor's cross inoculation experi- 

 ments appear to be fairly conclusive, but the number 

 of monospore infections which he made is epiite 

 small. It is not altogether improbable that more ex- 



plate 1 1 



Figs. 88 to 90. Germinated resting spore and zoospores 

 of O. varians. Exit tube passing through empty male 

 thallus. Shanor, I.e. 



Figs. 91 to 93. Echinulate, knobby and spiny resting 

 spores of O. Saprolegniae. Cornu, "1-2 ; Petersen, '09, '10; 

 and Shanor, '39b, respectively. 



Fig. 94. Resting spore of O. echinata. Petersen, '09, '10. 



Figs. 95 to 97. Smooth resting spores with attached male 

 thalli of O. Saprolegniae var. laevis. Coker, '23. 



Fig. 98. Three parthenogenetic and one sexual resting 

 spore of O. incrassata with broad undulating exospores. 

 Cornu, I.e. 



Fig. 99. Greatly enlarged resting spore of O. major with 

 three male thalli. Maurizio, '95. 



Figs. 100, 101. Echinulate and knobby resting spores of 

 O. vexans. Barrett, I.e., and Shanor, '39b, respectively. 



Figs. 102, 103. Irregular lobed zoosporangium and 

 heterocont zoospores of O. irregularis. Constantineanu, 

 '01. 



Fig. 104. Fusiform zoosporangia of O. fusiformis. Peter- 

 sen, '09, '10. 



Fig. 105. Broad-spined resting spore of O. fusiformis. 

 Cornu, I.e. 



Fig. 106. Similar resting spore of O. minor. Sparrow, 

 '32. 



Fig. 107. Resting spore of O. index with echinulate male 

 cell. Cornu, I.e. 



Fig. 108. Large and small resting spore of O. fusiformis 

 (?). Small spore may possibly be androgenetie. Coker, I.e. 



Fig. 109. Resting spore of O. spinosa with spiny male 

 cell. Tokunaga, '33. 



Fig. 110. Knobby resting spore of O. Aphanomycis. 

 Petersen, '09, '10. 



Fig. 111. Spiny parthenogenetic resting spore of O. 

 Aphanomycis. Whiffen, '12. 



O. Pythii 

 (All figures after Butler, '07) 



Fig. 112. Three sporangia in a swollen spherical hyphal 

 tip; supporting hypha with a cross wall. 



Fig. 113. Mature sporangium. 



Fig. 114. Zoospores clustered at mouth of exit tubes. 



Figs. 115, 116. Bean-shaped, isocont zoospores with re- 

 fractive granules. 



Fig. 117. Spiny, parthenogenetic resting spores. 



Figs. 118 to 120. Stages in the formation of spines on 

 the resting spore. 



O. </ racile 



Fig. 121. Young parasite in a swollen lateral diverticu- 

 lum. Butler, I.e. 



Fig. 122. Sporangia and resting spores in short swollen 

 hyphal branches, Butler, I.e. 



