LEPTOMITALES 897 



Probably synonymous with this species is Rhipidium compaction 

 Matthews (1936: 292, pi. 25), which differs significantly from R. inter- 

 ruption only in having the oogonia minutely papillate in many instances. 

 R. compactum is not mentioned in Coker and Matthews' 1937 paper. 

 Matthews' (1936) description of it follows: 



Plants appearing on the substratum as small whitish pustules about 0.5-1 

 mm. in diameter. Individual plants composed of a main trunk, which may 

 or may not be branched, a large number of short secondary branches on 

 which the reproductive organs are borne, and a well developed system of 

 large branched often lobed rhizoids, which may extend into the substratum 

 up to a distance of about 725 \x. Main trunk unbranched or with as many 

 as 8 large branches, 60-83 \x in diameter by 99-214 u long, constricted slightly 

 at the base where the rhizoids originate. Short secondary branches 9-42 u. 

 (majority about 20 jj.) long, from the large trunk, constricted at their point of 

 origin bear the sporangia and oogonia, usually singly, occasionally two, very 

 rarely three. Sporangia 2-10 on a main branch, very variable in shape on 

 the same plant, globose to pyriform ones 33-36 < 42 \i, cylindrical ones 

 20-29 x 49-70 a. Zoospores (rarely produced in the laboratory) reniform, 

 biciliate, 6.4-8 X 11.2-12.8 a, monoplanetic. Oogonia borne on same plant 

 as sporangia and mixed with them, at times even arising from same short 

 branch that bears a sporangium, spherical, 26^0 y. in diameter, wall thin, 

 smooth or usually with minute papillae. Oospores one to an oogonium, 

 29-33 [i. in diameter, wall at maturity sculptured and about 6.6 [i thick. 

 Antheridia one to each oogonium forming a tube to the oosphere and borne 

 on a long antheridial stalk arising from same plant but not from branch 

 bearing the oogonium or in some cases perhaps from a separate plant. 



On huckleberry and Amelanchier fruits, in Mountain Lake at Mountain 

 Lake, Giles County, Virginia, July and August 1936. 



The following variety and form were described by Forbes and 

 Kanouse, respectively. Variations in the species are so common, 

 however — far more striking than any formal diagnosis can depict — that 

 at the moment the character of the sex organs alone seems of important 

 taxonomic value. Although the variety and form are recorded here for 

 reference, they are not recognized. 



Rhipidium europaeum (interruptum) var. compactum Forbes 

 Trans. Brit. Mycol. Soc, 19: 234, pi. 10, fig. 11. 1935 

 "Thallus of a very short, broadly cylindrical basal cell bearing a large 

 number of broad, subdivided lobes, which spread out and around the 



