156 THE SAPROLEGNIACEAE 



variety unites in all degrees both the above methods of sporangial arrange- 

 ment, as is also the case in Humphrey's sterile plant (which is probably 

 the same as ours), first mentioned on p. 133 of his monograph, there is 

 little ground for taking this distinction seriously. The other differences 

 might easily come within the limits of variation of a single species, from 

 analogy with other Saprolegniaceae, and carry no conviction, especially 

 as Lindstedt seems never to have seen D. monosporiis , with which he com- 

 pares his species. 



EUROPEAN SPECIES NOT YET FOUND IN AMERICA 



Dictyuchus monosporus Leitgeb. Jahrb. f. wiss. Bot. 7: 357, pi. 22, 

 figs. 1-12, pi. 22,, figs. 1-8. 1869. 



This has been reported from America only by Pieters (in Kauffman, 

 '15), but we are treating his plant as D. Magnusii, which see. The following 

 is adapted from Fischer ('92, p. 362) : 



Growth thick, 1-1.5 cm. broad, with flaccid main hyphae up to 

 60iA thick. Sporangia terminal, either long, thread-shaped and little 

 or no thicker than the threads, or long clavate, 250-950^1 long, i8-37ix 

 broad, often containing only a single row of spores; proliferating by 

 repeated sprouting from the side below to form a sympodium. Spores 

 bean-shaped, 9-iosj, thick. Oogonia terminal, single, on long or short 

 branches of the main threads, spherical, 251J. in diameter; the wall uneven 

 and without pits. Antheridia always present, usually several to each 

 oogonium, borne on slender branches of diclinous origin which often 

 completely enwrap the oogonium. Eggs single, spherical, smooth, cen- 

 tric; germination not known. 



Cultivated on insects, or with ease on twigs, or on bulbs of hyacinth, 

 calchicum and tulip. 



According to Cornu the plant grows well on twigs and forms very 

 long threadlike sporangia with spores in a single row. The number of 

 spores is often large — up to 300 (Leitgeb), up to 600 (Cornu). Accord- 

 ing to Leitgeb sporangia are borne both on the threads which bear oo- 

 gonia and on the more slender male ones. Whether really dioecious or 

 not is not stated. [Above is from Fischer]. 



Leitgeb had an interesting experience with this plant. For the first 

 tw^o months of culture the spores escaped normally while the sporangia 

 were attached to the threads, the empty sporangia falling off" afterward. 

 After this period most of the sporangia fell ofif while still full, as in our 

 D. sterile, and in this condition the great majority of them sprouted as 

 in Aplanes. After another half month the sporangia of all cultures 

 failed to mature normal spores, the protoplasm of the spores dying soon 

 after they were formed. He thinks this abnormal behavior must have 

 been due to some peculiar diseased condition that he was not able to 

 e.xplain. 



