310 Algae. — Eumycetes. 



Monostroma sostericolum Tilden; M. pulchrum Farl.; M. fuscum 

 Wittr. ; M. latissimum Wittr. ; M. Vahlii J. Ag. ; Bryopsis corymbosa 

 J. Ag. ; B. plumosa f. corticulans (Setch.) nov. nom. {B. corticulans 

 Setch.); Rhisoclonium arenosum Kütz.; Chaetomorpha confervicola 

 De Toni; C. antennina Kütz.; Boodlea siamensis Rbld.; Sargassum 

 Grevillei J. Ag. ; 5. Sandei Rbld., 5. gracillimum Rbld., S. cervicorne 

 Grev. ; Ectocarpus siliculosus Dillw. f. varians Kuckuck; Acrochae- 

 tium crassipes Borg.; Wrangelia penicillata Ag.; W. purpurifera 

 J. Ag. ; Gracüaria lingula J. Ag.; Champia Sonata J. Ag.; Antitham-' 

 nion applicitum J. Ag. ; Hildenbrandtia rosea Kütz. Jongmans. 



Stevens, N. E., Some factors influencing the prevalence 

 of Endothia gyrosa. (Bull. Torrev bot. Club. XLIV. p. 127—144. 

 5 Textfig. 1917.) 



The contents of this paper are summarized by the author as 

 follows. Endothia gyrosa, which has a wider known ränge in 

 America than any other species of the genus, is undoubtedly 

 indigenous, having first been collected by Schweinitz nearly a 

 Century ago. 



Although the fungus is found in widely separated localities in 

 the United States it is abundant only in the Southeastern 

 States. Range maps, of this and other American species of 

 Endothia based on two 3 T ears collecting by Dr. C. L. Shear and 

 the writer have already been published. 



Inoculation experiments conducted in 1914 and 1915 showed 

 that E. gyrosa would under certain conditions grow and winter 

 over beyond the northeastern limits of its known ränge as well as 

 within the region where it is abundant. 



These inoculation experiments emphasized the importance of 

 the water supply and of the condition of the host in the growth of 

 the fungus. 



E. gvrosa grows most readily on injured tissue which does not 

 dry out immediately but remains living for some time, such as 

 stubs of cut limbs or injured roots. 



The temperature of the Southern States is undoubtedly 

 more favorable for the growth of E. gyrosa than that of the States 

 farther north. 



The northern boundary of the region where this fungus is 

 abundant does not, however, agree closely with that of any of the 

 temperature regions. 



It is not perceptibly more abundant in the areas of nine to 

 twelve months Vegetation than it is in areas of seven months 

 Vegetation. 



Much of the area where E. gyrosa is abundant is in or south of 

 the region of 25 inches rainfall, April to September, inclusive. It is, 

 however, very abundant in Tennessee, Kentucky and Indiana, 

 where the rainfall is less than 25 inches for this period. 



Although there are no sudden changes in climate in going 

 from north to south in the eastern United States, there is a fairly 

 definite division into an area where E. gyrosa is abundant and an 

 area where it is rare. 



This seems to indicate that factors other than climate affect 

 the prevalence of this fungus. 



The chief factor in the greater abundance of E. gyrosa seems 

 to be increased opportunity for infection. 



