Mar. 4. 1918 Wilt Diseases of Okra 531 



to the confusion existing in the genera Verticillium and Acrostalagmus, a 

 discussion of the interrelations of these form groups is necessary at this 

 time. 



Among those writers who have obtained and described Acrostalag- 

 mus-like fungi may be cited the following: Van Hook (27) discusses a 

 wilt disease of ginseng (Panax quinque folium) which he found associated 

 with a vascular-inhabiting fungus. It is said to closely resemble Acro- 

 stalagmus alhus Preuss. Rankin (20) renamed the ginseng-wilt fungus 

 "Acrostalagmus panax" Rankin, without giving a technical description 

 of the fungus or stating reasons for the change. Whetzel and Rosen- 

 baum (28), in mentioning this disease of ginseng, attribute it to a species 

 of Acrostalagmus. Gueguen (10) describes a new species of Acro- 

 stalagmus causing a wilt disease of the China aster Reine-Marguerite 

 (Aster sp.), and to this fungus he gave the name A . vilmorinii. A variety 

 of this organism he later mentions (11) as associated with a disease of 

 fruits of the cacao (Theobroma cacao). Lawrence (15) attributes a new 

 disease of black raspberry (Rubus occidentalis) — that is, the bluestera 

 disease — to a species of Acrostalagmus, for which he proposes the name 

 "Acrostalagmus caulophagus." Rankin (21), in a preliminary report of 

 a thrombotic disease of maple trees (Acer spp.), mentions that a species 

 of Acrostalagmus is associated with the trouble. 



Corda (9, p. jj) established the genus Acrostalagmus to accommodate 

 an organism, A. cinnabarinus , which was said to differ from Verticillium 

 by forming its spores in heads at the tips of the conidiophores. Hoffman 

 (is) has rightly explained the complicated structure of the sterigma as 

 represented by Corda, and likewise the collection in heads of the singly 

 abscissed conidia. The conidia are held together by virtue of an hygro- 

 scopic slime, which takes up water in the presence of a sufficiently moist 

 atmosphere, forming a sphere of water at the tip of each sterigma. In 

 these water droplets the conidia are observed to float freely. With ex- 

 cess moisture the drops rupture and the conidia slip down the conidio- 

 phore. However, in the absence of moisture the conidia cling tenaciously 

 to the tips of the sterigma in the form of irregular rounded masses of 

 varying sizes. If such material is placed under a dry cover slip without 

 being allowed to come in contact with the latter, and examined micro- 

 scopically while a small water drop is brought into the vicinity of the 

 dry spore head, the spore aggregate will be seen gradually to round up and 

 the conidia to float more or less actively within the spherule (PI. 17, B,D), 



In the genera Acrostalagmus and Verticillium we now have the follow- 

 ing contradictory and imperfect characterization and limitation of forms. 

 In Verticillium the singly abscissed and characteristically singly borne 

 conidia may adhere in the presence of moisture, forming terminal heads — 

 that is, water droplets containing conidia. In Acrostalagmus the 

 conidia, characteristically united in heads, soon separate if the humidity 

 of the environment is in excess of the maximum for the moisture drops 



