286 Journal of Agricultural Research voi. iv, N0.4 



In the absence of more definite information the evidence given in 

 Table I might be used in support of the theory sometimes advanced that 

 the ciHa are of peripheral origin; but in the present instance at least it 

 can be regarded only as an interesting correlation, since, as has already 

 been pointed out, the cilia are put forth from the blepharoplast by a 

 process of gradual elongation. 



Each spore contains a single large central vacuole lying in contact with 

 the nucleus and on the side toward the more pointed end of the spore 



(PI. XLVI, fig. 4, II)- 



The mitochondria are arranged in the zoospore at the periphery (PI. 

 XLVI, fig. 2). It is interesting to note that before cleavage furrows have 

 pushed through the dividing protoplasm of the sporangium the mito- 

 chondria have already arranged themselves at what is to be the peri- 

 phery of the future spore (PI. XLV, fig. 3). 



After coming to rest, the zoospore rounds up and undergoes certain 

 changes preparatory to germination. Vacuoles develop (PI. XLV, fig. 13), 

 and karyokinetic nuclear division occurs (PI. XLVI, fig. 15, 16, 17). One 

 or usually two germ tubes develop (PI. XLVI, fig. 3, 14, 17), forming a 

 mycelium. The nuclei continue to divide within the spore and migrate 

 into the mycelium, but divisions do not occur in the hyphge until they 

 have become mature (PI. XLVI, fig. 3). 



As the study of oogenesis is approached, it appears that both the 

 antheridium and oogonium are multinucleate. The nuclei originate by 

 karyokinesis in the parent hyphae and migrate to the reproductive organs 

 exactly as in the asexual stage. No divisions have been found to occur 

 in either the antheridium or oogonium, although thousands have been 

 sectioned and studied (PI. XLV, fig. 8, and XLVIII, fig. 2, 3). After 

 the requisite amount of material has been accumulated, the organs are 

 cut off by cross walls. An eccentric cavity develops in the oogonium, 

 so that the nuclei are arranged in a zone near the periphery (PI. XLVIII, 

 fig. 9). The vacuole then disappears; in its place there develops an area 

 which takes the stain more densely than the surrounding cytoplasm, and 

 a single nucleus comes to be within this area (PI. XLVIII, fig. 8). In the 

 meantime, the remaining egg nuclei undergo degeneration without division 

 in the region where the wall of the oosphere is to appear (PI. XLVII, fig. 

 2,5, and XLVIII, fig. 5, 8). A receptive papilla forms on the antheridial 

 side of the egg, and a passage way is opened from the antheridium through 

 which a single nucleus and a considerable quantity of cytoplasm pass into 

 the oosphere (PI. XLVII, fig. 2, 5, 6, and XLVIII, fig. 8). The remain- 

 ing antheridial nuclei degenerate (PI. XLVII, fig. 2, 5, and XLVIII, fig. 

 8). The functional antheridial nucleus takes a position within the denser 

 staining area at the center of the egg beside the egg nucleus and eventually 

 fuses with it (PI. XLVII, fig. i, and XLVIII, fig. 5, 6, 7, 10). 



There appears to be a certain am.ount of latitude as to the order in 

 which some of the foregoing steps may occur. Sometimes the central 



