Febeuabt 13, 1914] 



SCIENCE 



257 



place of a filamentous mycelium, the production 

 of a filamentous mycelial growth devoid of 

 sporangia, and a partial change at least toward 

 the dioecious condition. Some of these variants 

 are surely temporary conditions for they tend 

 eventually to revert to the normal type. Others 

 may be more permanent but have not been suffi- 

 ciently investigated. All, however, tend partially 

 at least to reproduce the new characters and some 

 have for several sporangia! generations kept their 

 peculiarities in gross cultures during the few 

 months it has been possible to propagate them. 

 Many of them would undoubtedly be described as 

 distinct species by specialists in the group. 



The Development of Amanitopsis vaginata and 

 Lepiota clypeolaria: Geo. F. Atkinson. 

 Amanitopsis vaginata. — The primordium of the 

 pileus arises in the middle of the upper part of 

 the young carpophore as a dome-shaped area. 

 This soon differentiates into an upper portion, 

 the pileus primordium; and a lower one, the 

 hymenophore primordium. By surface and mar- 

 ginal growth (the latter being epinastie) through 

 the enveloping fundamental tissue, the pileus is 

 formed. By downward and obliquely inward 

 growth of the hymenophore through the funda- 

 mental tissue toward the stem fundament the 

 primordial tissue of the lamellse is formed. This 

 gradually becomes differentiated into the pri- 

 mordia of the lamellse, the trama of the gills be- 

 ing continuous with the trama of the pileus and 

 the surface of the stem. There is no interaal an- 

 nular gill cavity as in Agaricus, Lepiota, etc. The 

 fundamental tissue enveloping the primordia of 

 pileus, hymenophore and stem is the ' ' universal 

 veil," or in fact gives rise to it at a quite late 

 period in the organization of the pileus when an 

 outer zone of the developing pileus changes into a 

 gelatinous cleavage layer. 



Lepiota clypeolaria. — Before any evidence of 

 internal differentiation of the primordia of the 

 pileus, hymenophore and stem, the young carpo- 

 phore presents an outer duplex zone, the "uni- 

 versal veil ' ' of Fries. The inner portion of this 

 zone consists of a thin layer of subpseudopa- 

 renchymatous cells, the outer portion of long 

 radially extending threads. After the origin of 

 the stem and pileus fundaments, this ' ' universal 

 veil" is for some time separated from the pileus 

 and stem by a zone of loose fundamental tissue. 

 In the further differentiation of the pileus the 

 surface threads grow through this intermediate 

 zone of fundamental tissue and tie into the inner 



zone of the ' ' universal veil ' ' so that the latter be- 

 comes ' ' concrete with the surface of the pileus, ' ' 

 no cleavage layer being formed. 

 A Preliminary Note on Spore-formation in Cya- 

 thus: Guy Bisbt. 



Practically no work has been done in recent 

 years on this genus, making an examination of 

 some interest. The nuclear divisions in the 

 basidium is followed in CyatJius vernicos%s by a 

 nuclear division in the spore, making this species 

 binucleated, whereas in Cyatltus stercoreus the 

 spores remain uninucleated. This cytologieal fea- 

 ture should be of advantage as a systematic cri- 

 terion. HyphSB growing from germinated spores 

 have been observed, in forming anastomoses, to be 

 met by a short protuberance from the hyphse ap- 

 proached, apparently responding to some sort of 

 attraction. 



Variation in the Sporangia and Spores in the 

 SaprolegniacecE and its Bearing on their Classifi- 

 cation,: W. C. COKEB. 



Original observations on such variations are re- 

 ported and the literature examined. It is con- 

 cluded that while there is great variation in size, 

 arrangement and behavior of both spores and 

 sporangia, these (with possibly a single exception) 

 are not of a character to confuse our present con- 

 ception of genera in this family. 

 A Peculiar Water Mold: W. 0. Cokeb. 



A new species is reported from Chapel Hill, N. 

 C, that exhibits in a confusing way certain of the 

 reproductive peculiarities of Achlya and Sapro- 

 legnia. The spores on emerging swim away in 

 part while others remain attached to the spo- 

 rangium tip. 



Occurrence and Periodicity of Water Molds at 

 Chapel mil, N. C. : W. C. Cokeb. 

 The results of about 450 collections are given, 

 showing the relative abundance of the species 

 found and their periodicity in so far as it exists. 

 About 20 species are discussed. 

 Foliage Resistance of Different Varieties of Po- 

 tatoes to Phytophthora infestans: I. E. Melhus. 

 A study has been made of the varietal resist- 

 ance of potatoes to Phytophthora infestans by 

 artificially infecting the foliage. Varieties re- 

 puted to be either resistant or susceptible were 

 grown in the greenhouse and subjected to favor- 

 able conditions for Phytophthora infection. The 

 conidia of the fungus were germinated in water 

 at optimum temperature conditions (about 13° C). 

 The resulting zoospore suspension was sprayed in 

 the lower surface of the leaves of the healthy. 



