132 



THE SAPROLEGNIACEAE 



main hyphae and from the oogonial stalks, and b>- the presence of pits 

 in the oogonial wall. Hildebrand's original form is described as ha\'ing 

 the antheridial branches coming from the oogonial stalks, and in this 

 and the unpitted walls differs from ^4. deBaryana. DeBary's A. gracilipes 

 is certainly a very different looking plant from the present species, 

 and may be quite distinct from A. polyandra Hildebrand. 



Possibly representing a peculiar form of the present species is a 

 slide prepared by us in the fall of 1903, before we were much interested 

 in this group. The pitted oogonia and the antheridia are borne in about 

 the same way, but the plant seems so abnormal that we are not at all sure 

 what it is. The walls of the hyphae, the stalks, the oogonia and even the 

 antheridia are mostly very thick and in places so thick as almost to close 

 the lumen, reaching a thickness in places of 7.5;i.; the eggs are all going to 

 pieces, but their walls show them to be mostly 22-24;x thick, a few up to 

 301J.. (The plant is not Aplanes androgynous or A. Treleaseanus, which 

 have thicker walls than other species). The stalks flare greatly at the top 

 and the wall separating the oogonium is often so far up as to cut off a 

 lower section of the oogonium, thus including it in the stalk. Such queer 

 structures can only be abnormal, and careful examination of the oogonial 

 contents show amongst the varied detritus certain minute, spherical bodies 

 of constant structure and appearance. They may be and probably 

 are the parasite causing the trouljle. They are not at all like any of the 

 chytridiacean parasites of the family. May they not be the amoeboid 

 parasite Vampyrellidium vagans Zopf, which has been insufficiently 

 investigated? (Schenck's Handb. 4: 540 and 565. See reference to 

 this by Fischer '92, p. 325). 



18. Achlya oblongata deBary. Bot. Zeit. 46: 646, pi. 10, figs. 7-9. 1888. 



Plates 46 and 47 



Mycelium rather stout and vigorous; sporangia subcylindric to 

 fusiform, pointed; dictiosporangia not rare; spores small, about 910. in 

 diameter. Gemmae oval like the eggs or often linear by the division 

 of the main hyphae. Oogonia very large, typically oval to pyriform, 

 rarely nearly spherical, 40-1 501J. in diameter the short way, borne usually 

 on moderately long lateral branches, at times terminal on main branches, 

 rarely intercalary; wall thin, hyaline, without pits. Eggs 1-28 or 30, 

 rather small, 20-3011., most about 271X in diameter, subcentric, with a 

 lunate (in section) sheath of oil droplets nearly surrounding the proto- 

 plasm; usually arranged loosely in the oogonium and not filling it, at 

 first very dark, rarely maturing. Antheridial branches delicate and 

 slender, always diclinous and not traceable to threads bearing oogonia; 

 antheridia on every oogonium, usually numerous, small and tuberous, 

 no fertilizing tubes seen. 



