50 THE SAPROLEGNIACEAE 



by Pieters on this species in various media see Am. Jour. Bot. 2: 529. 

 1 91 5. Pieters also writes us of an interesting observation of his on 

 this species, that in plates of pea agar that had become infected with 

 bacteria the oogonia were very abundantly produced on the hyphae 

 along which the bacteria were thickest, but not along the hyphae where 

 the bacteria were few. 



Next to Pringsheim 's, which is ill-defined, the most authentic de- 

 scription of the species may be taken as that by deBary ('88, p. 616), 

 who writes as follows (translation) : 



"Main threads straight, tense. Primary sporangia slender, clavate- 

 cylindric. Antheridial branches androgynous, forming antheridia on all 

 the oogonia, almost always arising near and springing from the same 

 stalks as the oogonia to which they are attached or from neighboring 

 ones. Oogonia usually borne on racemosely arranged, bent or straight 

 short branches which are about as long as the diameter of the oogonia; 

 the main hyphae from which these spring ending in an oogonium, or a 

 sporangium, or a sterile point. Oogonia spherical, smooth, with several 

 large pits in the membrane. Oospores from one to over 30, mostly 5-10 

 in an oogonium, centric. Antheridia bent-clavate, with the concave 

 side applied to the oogonium." 



Fischer gives the eggs as i6-22[i thick. Minden ('12, p. 608) thinks 

 that 5. semidioica of Petersen is the same as 5. monoica, and to all appear- 

 ances he is right. According to Lindstedt ('72, p. 64) Achlya intermedia 

 Bail ( '61 ) is a synonym of Biplanes saprolegnioides. For other illustrations 

 of 5. inonoica see Reinke ('69), pi. 12; deBary ('81), pi. 5, figs. 11-19, 

 and pi. 6, figs. 1-2; Pringsheim ('58), pis. 19 and 20 ; Ward ('83), pi- 

 22, figs.ii-22; Rothert ('88), pi. 10, fig. 14; Massee ('91), pi. 5, figs. 

 91-93; also Dangeard and Claussen as cited below. 



Fertilization has been convincingly proved for this species by Claus- 

 sen ('08). His results may be summarized as follows: Young oogonia 

 arc full of protoplasm and contain many nuclei; degeneration of both 

 protoplasm and nuclei takes place from the center outward until there 

 remains only a rather thin layer of peripheral protoplasm containing 

 comparatively few nuclei; these remaining nuclei now divide once my- 

 totically at the same time, showing about 10-14 chromosomes; of the 

 resulting nuclei all degenerate except one for each egg. A centrosome 

 with radiating fibers is observed with the nucleus in this division in the 

 oogonium, and it remains visible in the nucleus of the young egg. It is 

 not to be observed at time of fusion of the egg and sperm nuclei. The 

 antheridia contain a varying number of nuclei which divide simultane- 

 ously with those of the oogonia; fertilizing tubes are formed which are 

 simple or much branched. One male nucleus is discharged into each 

 egg and soon reaches the egg nucleus, the two remaining pressed to- 



