896 AQUATIC PHYCOMYCETES 



swollen, contorted, gnarled, divided into broad branchlike lobes or 

 appressed and peltate, up to 800 u. broad, the lobes attaining a breadth 

 of 1 50 \x or more, the wall variable, often 20 \x thick, sometimes roughen- 

 ed; cylindrical branches numerous, generally arising from the apices of 

 the lobes of the platform, constricted and pseudoseptate at the base, 

 more or less constricted and often pseudoseptate along their length, 

 7-14 [i. in diameter by 100-500 \x long, rarely branching, holdfasts 

 extensive, branched; sporangia generally single, terminal, borne on 

 short subspherical segments or sympodially arranged on long cylindrical 

 branches, ovoid to ellipsoidal, sometimes nearly spherical, 40-78 u, long 

 by 18.5-47 \x in diameter, papilla apical, wall smooth, very thin and 

 collapsing after discharge or stout; zoospores reniform, 12-13 \x, 

 bifiagellate, contents with numerous refractive granules; antheridium 

 small, 19 [x long by 15 \x wide, somewhat clavate or spherical and 

 appressed distally to the lower part of the oogonium, borne at the tip 

 of a long slender branched or unbranched often tortuous hypha of 

 diclinous, monoecious, or dioecious origin; oogonia borne like the 

 sporangia on the same plant, pedicellate, spherical or pyriform, 40-60 \x 

 in diameter, wall stout, smooth, colorless; oospore spherical or ellip- 

 soidal, 27-50 [x in diameter, colorless or slightly golden, not filling the 

 oogonium, the inner wall thin, smooth, the outer very thick (up to 1 7 jx) 

 and raised in an irregular series of broad ridges and protuberances, 

 stellate in section view, germination not observed. 



Forming dense pustules, sometimes mats, on fruits and twigs. On 

 twigs, Cornu (he. cit.), France; fruits and twigs, Minden (he. cit.), 

 Laibach (1927:599), Behrens (1931:745, figs. 1-33), plum twigs, 

 Hohnk (1935: 218), Germany; twigs of alder, birch, fir, H. E. Petersen 

 (1909: 389; 1910: 526, fig. 4a, e), twigs, apples, Lund (1934: 36, fig. 16), 

 Denmark; fruits, Boedjin (1923: fig. 1), Holland; fruits, Kanouse 

 (1926: 113, pi. 1, fig. 2; 1927: 341, pi. 48, figs. 27-33, 39), twigs (Mich- 

 igan) United States; apples, Valkanov (1931a: 366), Bulgaria; rose 

 fruits, Forbes (1935a: 234, fig. 1 ; 1935b: 3), fruits, twigs of Era.xi/ius, 

 Sparrow (1936a: 459, pi. 20, figs. 6, 10), fruits, Waterhouse (1942: 321), 

 Great Britain; twigs of Primus grayana, Indoh (1953: 31, figs. 17-18), 

 Japan. 



The cytology of the species (see p. 865) has been studied by Behrens 

 (1931). 



