GROUP 1. THALLOPHYTA: ALGM : RHODOPHYCE5]. 



269 



consist essentially of a unicellular carpogoniam (with a trichogyne) 

 together with one or more specially differentiated auxiliary cells. 

 In some cases (e.g. Dudresnaya coccinea, Squamariaceae), the carpo- 

 gonium and the auxiliary cells are not developed in the same 

 procarp, bat in distinct organs. 



Whether the procarps be unicellular or multicellular, the carpo- 

 gonia agree in that the trichogyne remains closed, and further, 

 in that the protoplasm of the carpogonium does not undergo re- 

 juvenescence to form a distinct 

 female cell (oosphere) as is the 

 case in the oogamous Algae. 



The carpogonium is (except in 

 the Bangiaceas) developed from the 

 terminal cell of a lateral appen- 

 dage; in some cases (e.g. Polysi- 

 phonia fastigiata and nigrescens) the 

 lateral appendage is a leaf, the 

 whole or part of which goes to 

 form the procarp ; in the Coral- 

 linaceae the procarps are aggre- 

 gated in receptacles. 



The sexual process consists in 

 the fusion of the protoplasmic con- 

 tents of a spermatium with those 

 of a trichogyne. The spermatiura 

 is brought by the water into con- 

 tact with the projecting trichogyne 

 to which it adheres, the sperma- 

 tium being at this time covered 

 with a cell-wall ; the intervening 

 cell-walls are absorbed at the 

 point of contact, and the proto- 

 plasm of the spermatium enters 

 the trichogyne. 



The product of fertilisation is a fructification termed a cysto- 

 carp, consisting of a number of carposporangia. The cystocarp is 

 developed either directly or indirectly from the carpogonium : 

 directly, when the procarp is unicellular ; indirectly, when it is 

 developed from both carpogonial and auxiliary cells : the tricho- 

 gyne takes no part in the development of the cystocarp, being 

 shut off by a septum. 



FIG. 194. Sexual organs of Nemalion 

 ( x 300) A ends of branches bearing a 

 unicellular procarp t-o, and a group of 

 antheridia s ; the trichogyne (t) of the 

 procarp has two spermatia (s) adhering 

 to it. .B early stage in the development 

 of the cystocarp ; the fertilised carpo- 

 gonium is undergoing growth and 

 division. C nearly mature cystocarp, 

 consisting of a number of short fila- 

 ments each terminating in a carpospo- 

 rangium. The development of the 

 cystocarp is direct. 



