314 Journal of Agricultural Research vol. xx.No.4 



P. calami, P. hipuridis, P. spargani, and P. speciosum, germinate, per- 

 haps, in a manner similar to P. menyanthis , in which, according to Clinton 

 (5) , the outer wall is ruptured by the elongating protoplast, dehiscence of 

 the zoospores taking place at the tip of the protrusion. The absence of 

 any indication of lids from the spores of all species of Urophlyctis exam- 

 ined may be of taxonomic significance, although this can not be deter- 

 mined until more reliable results have been obtained in the germination 

 of the spores. It would be interesting, too, to determine from living 

 material the positional relation between the zone of haustoria and the lid 

 in those species where both appear to be present, as seems to be the case, 

 for example, in P. menihae and P. zeae-maydis. 



The more striking recorded departures of a number of species of Physo- 

 derma from the general thallus structure of the two species of Urophlyctis 

 investigated by us remain in need of explanation. One of the departures 

 is found in the septation of turbinate cells and in the fate of the different 

 segments. As has been pointed out, in Urophlyctis alfalfae and U. pluri- 

 annulatus the production of secondary turbinate cells always starts with 

 the delimitation of peripheral segments that involve portions of the 

 parent cell wall, most frequently subapical or lateral and occasionally 

 subbasal. The distinction between a smaller basal cell and a larger 

 distil cell, made by Biisgen for Physoderma butomi (3) and by Clinton 

 (5) for P. maculare, is thus without significance here; while their 

 accounts of the origin of the resting spore from the proximal cell are 

 directly at variance with developments in U. alfalfae and U. pluriannu- 

 latus, in which the resting spore is invariably developed from the large 

 multinucleate residue not involved in peripheral segments. Ludi (15) 

 figured the " Sammelzellen " of P. menyanthis with 1 or 2 transverse 

 septa and represented the resting spore as being attached to the 

 distil segment thus delimited by a filament of considerable length. 

 According to this writer's account, the resting spore here is not always 

 terminal, but by itself proliferating a "Sammelzelle" it often appears 

 as an intercalary structure associated with two "Sammelzellen." Tis- 

 dale's (jj) account of P. zeae-maydis presents even more points of 

 difference, showing structures consisting of two to four lobulate seg- 

 ments set off by transverse septa, these segments, with the exception of 

 one, capable of forming a resting spore either directly or at the end of a 

 fiber. In this form, organization and development would appear to be 

 of a rather miscellaneous type, contrasting sharply with the definite 

 sequence of growth found in the two plants figured in this paper. 



Reference has been made elsewhere to Biisgen's figures of Physoderma 

 (Cladochytrium) flammidae, in which the resting spore is represented as 

 being attached to the "Sammelzelle" by the side bearing the haustoria. 

 Another detail worthy of note in the same figure of Biisgen's is the 

 length of the hypha connecting "Sammelzelle" and resting spore, ap- 

 proximating as it does half the length of the resting spore. In Cornu's 



