Nos. 451-452.] STUDIES ON THE PLANT CELL. 589 



The distribution of the plastids in the eggs of Algae may be 

 so general that the entire cell is colored as in Fucus, Volvox and 

 Sphaeroplea. Or, the plastids may be largely or wholly-wkh- 

 drawn from some portion of the egg. It is usual for eggs 

 retained within the parent cell (oogonium) to present a colorless 

 area of protoplasm that becomes the point at which the sperm 

 fuses with the egg. Such a hyaline region is called the recep- 

 tive spot and is generally situated (see Fig. lib] at the side of 

 the egg nearest the pore or opening in the oogonium through 

 which the sperms enter. Excellent illustrations are presented 

 among the Algae in Vaucheria (Oltmanns, '95), CEdogonium 

 (Pringsheim, '58, Klebahn, '92) and Coleochaete (Pringsheim, 

 '60, Oltmanns, '98). It has been suggested that the receptive 

 spot is related to the clear ciliated end of the ancestral motile 

 gamete and zoospore but the structures have not been critically 

 compared to determine the precise character of their proto- 

 plasmic structure and development. The receptive spot in 

 some forms (Vaucheria, CEdogonium, Fig. 1 1 b") lies directly 

 under the opening that is formed in the oogonium and its 

 protoplasm is probably concerned with the fermentative action 

 that destroys the wall at that point. 



The red Algae (Rhodophyceas) do not have eggs although in 

 their sexual evolution they are at the level of heterogamy. The 

 female gamete (carpogonium with its trichogyne) is a cell homol- 

 ogous with an oogonium and its protoplasmic contents corre- 

 spond to an egg, but the protoplast never withdraws from the cell 

 wall to lie freely as a naked mass of protoplasm within the 

 structure. But the general agreement of the carpogonium and 

 trichogyne with the oogonium and its neck like extension in 

 Coleochaete seems to determine without doubt the homologies 

 of the former. 



There are very few eggs among the fungi that are strictly 

 comparable to those of the Algae. Monoblepharis (Thaxter '95a) 

 however unquestionably furnishes such an example. But the 

 eggs of the Saprolegniales and Peronosporales are probably in 

 the author's opinion not directly derived from those of Algae. 

 They are either a peculiar form of sexual cell called the cceno- 

 gamete (Davis :oo and 103) or closely related to this structure 



