DICTYUCHUS 153 



same as the first mentioned of the two sterile plants noted by Humphrey 

 on p. 133 of his monograph, though he does not mention the deciduous 

 sporangia. Dr. I. F, Lewis tells us that he has seen a similar form in 

 \'irginia, and Weston ('19) has described a second swimming stage in 

 a sterile plant that he finds in Massachusetts. We have little doubt that 

 his plant is the same as ours, not only from its sterility, but because a 

 sporangium is shown nearly loosened from its hypha (fig. 19). Weston's 

 good figures of detail in the spores and their emergence should be con- 

 sulted. Both Tiesenhausen ('12, p. 289, figs. 15-18) and Minden ('12) 

 find a sterile plant in which the sporangia fall off, which is probably the 

 same as ours in both cases. Minden refers his sterile plant to D. mouo- 

 sporus, but this, of course, could not be convincingly done without a 

 knowledge of the sexual organs. 



The situation is indeed interesting and perplexing. Leitgeb ('69) 

 found that sporangia appeared on both the male and female threads 

 of D. monosporus; he also found a sterile plant (species unknown, perhaps 

 the same as ours) in which only sporangia were formed during four months' 

 cultivation. On the other hand, Lindstedt never found any sporangia 

 on male or female threads of D. Magnusii, and speaks of his plant as 

 trioecious for that reason (1. c, p. 16). It seems to us to be \ery signifi- 

 cant that in all cases a Dictyiichus that started out to be sterile has 

 remained so consistently, and thus has never been proved to be the same 

 as a fertile species, while all fertile species have been fruitful from the 

 first. 



With the exception of D. polys poms, which is of more than doubt- 

 ful validity, all of the species are known to be diclinous, and it may be 

 that we have here a real dioecious plant (if so the only one in the family) . 

 In such case it might be possible that one of the sexes could come to oc- 

 cupy alone an extensive territory by asexual reproduction, with apparent 

 sterility as a result. This is, however, very improbable as in no other 

 species of the family is the presence of antheridia necessary for the ap- 

 pearance of the oogonial initials. We have at \-arious times put together 

 cultures from different sources in the Chapel Hill region in an effort to 

 settle this point, but always without result. If sexual reproduction 

 should ever be found in our plant and be similar to that of a known 

 species, its extreme sterility would still entitle it to recognition as a vari- 

 ety or race. 



Cultures from Xo. 13 of November 7, 191 2: 



In maltose 5%+ peptone .01%. Growth was fairly strong, but not over inch in diameter. 

 The protoplasm in many of the hyphae was segregated into little clumps, as in 

 Achlya hypogyna in several media. Many spores were formed. After two weeks the 

 culture was still alive, with many hyphae of normal appearance. 



