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



The distribution of the plastids in the cl;i;s ot Ali;;r may be 

 so general that the entire cell is colored as in l-'iu us. \dl\<)\and 

 Sphoeroplea. Or, the plastids may be lar-vly or uholh with- 

 drawn from some portion of the e-,-;. It is usnal tor e.i;i;s 

 retained within the parent cell (o()t;-onium ) to present a colorless 

 area of protoplasm that becomes the ])oint at whic h the sperm 

 fuses with the egg. Such a hyaline re,<;ion is called the lecej)- 

 tive spot and is generally situated (see l'"i,<;-. i xb) at the side of 

 the egg nearest the pore or opening in the oogonium thr<uigh 

 which the sperms enter. Excellent illustrations are j)reseiUed 

 among the Algae in Vaucheria (Oltmanns, "(jS), (]Mog<>nium 

 (Pringsheim, '58, Klebahn, '92) and C'oleodia te ( Trin-sheim, 

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

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

 gamete and zoospore but the structures have not been critic ally 

 compared to determine the precise character of their proto- 

 plasmic structure and development. 1 he recepti\e spot in 

 some forms (Vaucheria, CEdogonium, Fig. 11/') lies directly 

 under the opening that is formed in the ocigonium and its 

 protoplasm is probably concerned with the fermentati\ e action 

 that destroys the wall at that point. 



The red Algai (Rhodophyccx) do not haxe eggs although in 

 their sexual evolution they are at the le\el of heterogamy. The 

 female gamete (carpogonium with its trichogyne; is a c ell homol- 

 ogous with an oogonium and its protoplasmic contents corre- 

 spond to an egg, but the protoplast nev er withdraw^ from the cell 

 wall to lie freely as a naked mass of proto[;lasin within the 

 structure. But the general agreement of the c arpo-onium and 

 trichogvne with the oogonium and its neck like extension in 

 Coleochate seems to deternune without doubt the h.miologies 

 of the former. 



There are very few eggs among the fungi that are strictly 

 comparable to those of the Alga^. Mon< .blepharis (Thaxter Vjsa) 

 however unquestionably furnishes such an example. But the 

 eggs of the Saprolegniales and I'eronosporales are probably in 

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

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

 gamete (Davis :oo and 103) or clo.sely related to this structure 



