PERONOSPORALES 1023 



have been observed (Sparrow, 1936a). In his material the first indication 

 of germination was a slight increase in the amount of the protoplasmic 

 contents and the appearance of faint shadowy areas of indefinite 

 shape in the thick hyaline wall. After twelve hours the large 

 reserve globule in the contents disappeared, the cential granular cy- 

 toplasm increased in size, and around the periphery of this cytoplasm 

 a large number of short spinelike protuberances appeared Fig. 88 J-L, 

 p. 1045). During the succeeding twenty-four hours the contents continued 

 to expand, at the expense of the refractive wall, and at the same time it 

 became densely granular. The "spines'" increased in breadth, until their 

 tips touched the inner wall of the oogonium. In another twenty- four 

 hours the contents almost reached the oogonial wall and the spines 

 again became only short peripheral attenuations. Subsequently, these 

 completely disappeared and the contents occupied the whole oogonium 

 (Fig. 88 M). A discharge tube was then produced, through which, 

 presumably, the contents were ejected (Fig. 88 N). Although the true 

 nature of these curious spines was not determined, it is possible that 

 they simply outline vacuoles. A similar process of germination has been 

 described by Blackwell (1943a) in Phytophthora cactorum. There, she 

 interpreted the spines as fine radiating passages in the endospore wall. 

 If this view is correct, it would suggest that the reserves of cellulose, 

 protein, and so forth, are being digested at different rates. 



The sex organs and oospores in Phytophthora are so like those in 

 Pythium that discussion of them is unnecessary. The production of 

 amphigynousantheridiain/'/H7op/;//;ora, however, is unique (see Fig. 901), 

 whereas the peculiar method of germination of the oospore in some 

 species of that genus is a feature shared with Pythiogeton(p. 1042). In 

 Phytophthora fischeriana, Hohnk (1936) says the oospore is apogamously 

 developed. 



SYSTEMATIC ACCOUNT 



PERONOSPORALES 



The aquatic members of the Peronosporales are all species of the 

 Pythiaceae. Their characters are those of that family as given below. 



