BLASTOCLADIALES 673 



because they are based on asexual plants only. Emerson (1941) treated 

 the relation of A. kniepii Sorgel to A.arbuscula in detail. He also estab- 

 lished two varieties of ' A.arbuscula that depend on differences in size of the 

 resting spores. Since intergrades between the varieties occur, this sep- 

 aration was mainly for convenience. In A. arbuscula var. arbuscula the 

 resting structures average 32-45 [i in width; in var. minor, 24-31 a. 

 These varieties are not maintained here, as Emerson and Wilson (1954) 

 doubt their validity on the basis of size alone. 



Allomyces x javanicus Kniep (pro sp.) 1 



Berichte Deutsch. Bot. Gesell., 47: 211, figs. 1-7. 1929 

 (Figs. 40 B, p. 616; 41 A-J, P, p. 622) 



Allomyces javanicus var. javanicus Emerson, Lloydia, 4: 135. 1941. 

 Allomyces javanicus var. perandrus Emerson, Lloydia, 4: 135. 1941. 



Basal cell conspicuous, variable in size, hyphae copiously sympodially 

 or dichotomously branched; zoosporangia ovoid or barrel-shaped, ter- 

 minal or catenulate, 60-80 \x long by 27-50 u. in diameter, with one or 

 several discharge papillae, zoospores ovoid, 11-12.5 \l long by 8-10 \x 

 in diameter; resting spores ovoid or subspherical, with rounded apex 

 and truncate base, 34.5-60 \x long by 23.5-35 jjl in diameter, the exospore 

 thick, olivaceous brown to tawny or reddish brown, 2 minutely punctate, 

 upon germination forming posteriorly uniflagellate planonts; sexual 

 plant similar to the asexual, gametangia somewhat irregularly arranged, 

 terminal, single, in pairs or catenulate and alternating, the male terminal 

 or, rarely, subterminal, cylindrical, with narrow apex, usually about 

 34.5 [jl long by 23.5 jjl broad when terminal, subtended by the some- 

 what larger, more ovoid female gametangium, which is usually about 

 51 [jl long by 33 \x in diameter, male gamete 4.8-6.3 \x long by 3.4-4.4 \l 

 wide, faintly orange to reddish, female gamete 9-1 1.5 \x long by 7.5-8.5 \i 

 wide, colorless, the biflagellate planozygote coming to rest to form the 

 new asexual plant. 



In soil, Kniep (loc. cit.), Java; United States; Mexico; Tangan- 

 yika; Burma; Fiji; Japan. 



1 Demonstrated by Emerson and Wilson (1954) to be Allomyces arbuscula X A. 

 niacrogynus, see p. 631. 



2 According to Emerson (1941). 



