On Allomyces, a new Aquatic Fungus. 
BY 
E. J. BUTLER, M.B., F.L.S. 
Imperial Mycologist, Agricultural Research Institute, Pusa, India. 
With Figures 1-18. 
AMONG the aquatic Phycomycetes few are more interesting than the 
members of the family Leptomitaceae of Schroeter, filamentous 
Oomycetes characterized by the filaments being segmented through the 
presence of successive constrictions, with oogonia, when present, containing 
a single oosphere surrounded by periplasm. The family was included by 
Schroeter with the Saprolegniaceae and Pythiaceae in the order Sapro- 
legniineae, but Thaxter (’ 06 , p. 324) subsequently pointed out that its 
affinities with the Pythiaceae must cause it to be transferred to the Perono- 
sporaceae if Pythium be united to the latter family. 
It is probable, however, that the Leptomitaceae are more primitive 
forms than either the Saprolegniaceae or Pythium , and I have suggested 
(’ 07 , p. 58) that they may show indications of affinity with the curious 
genus Monoblepharis and through it with the green Algae (Siphoneae or 
Oedogoniaceae). The number of forms known to belong to the family is 
small, and it is therefore of decided interest to encounter a new one with 
distinctive characters. 
The Fungus occurs in Pusa in still (but not stagnant) water, and in 
Poona in river water, in both cases growing on dead flies, &c., which have 
fallen in. The plants may be single or two or more may occur together, 
the growth presenting to the naked eye the familiar appearance of a Sapro - 
legnia colony. It can be readily isolated from accompanying Phycomy¬ 
cetes by suspending dead sterile flies or ants near the surface of a dish full 
of water in which a few sporangia ready to discharge are placed. It grows 
freely in such cultures, and is not much hindered by the development of 
Bacteria as in some of the allied forms. 
The plant consists of a distinct basal part formed of several very large 
cells, sometimes arranged in a single column, sometimes in a dichotomously 
branched system. From the distal end of this, whorls of more slender 
[Annals of Botany, Vol. XXV. No. C. October, 1911.] 
3 x 2 
