THE ALGJE 137 



in groups of four within a mother-cell. In a few cases, e.g. Chan- 

 transia, Monospores are formed, and very rarely the sporangia de- 

 velop more than four spores (Callithamnion dasyoides). 



Sexual Reproduction. The sexual reproductive organs are special 

 cells, Carpogonia, which are fertilized by non-motile male cells (Sper- 

 matia). The carpogonium may at once give rise to a mass of spores 

 (carpospores), or it may be associated with other cells into a multi- 

 cellular organ, the Procarp, which after fertilization develops into a 

 complicated spore-fruit (Cystocarp). The more important of these 

 forms will be taken up in connection with the special orders. As 

 in the Phaeophyceae, no resting-spores are produced, and both tetra- 

 spores and carpospores germinate as soon as they are ripe. 



Classification. There are two subclasses of the Khodophyceae, the 

 Bangiales, with a single order, Bangiaceae, and the Florideae, which 

 comprise the greater part of the class, and differ so much from the 

 Bangiales that the latter are sometimes considered to be more nearly 

 related to the Chlorophyceae than to the Florid ese. 



Bangiaceae 



The Bangiacese comprise a small number of simple Algae, which, 

 aside from their color, show certain resemblances to the Chlorophy- 

 ceae, and may perhaps connect these with the higher Rhodophyceae. 

 While most of them are marine, there are also a number of fresh- 

 water species. 



Plant-body. The plants are either filaments or very simple cell-plates, as 

 in Porphyra (Fig. 107), which except for its color closely resembles Ulva. The 

 cells contain a single large chromatophore and a single nucleus. No protoplas- 

 mic connections can be discerned between the cells. 



Reproduction. Non-sexual reproduction consists in the escape of the con- 

 tents of a thallus-cell, either directly, or after one or two preliminary divisions. 

 These monospores thus closely resemble the zoospores of many Confervaceae, 

 from which they differ in the absence of cilia. It is said, however, that slight 

 amoeboid, or creeping, movements have been detected, in which they are differ- 

 ent from the monospores of the Florideae. The sexual reproduction is also very 

 simple. Apparently any thallus-cell may become an oogonium (carpogonium). 

 There is no contraction of the contents, and a slight prominence is developed, 

 which perhaps represents the trichogyne, or fertilizing-tube found in the carpo- 

 gonium of the Floridea?, but also recalls the same structure in Coleochaete (Fig. 

 107 D). 



The antheridia (Fig. 107, C) are formed from vegetative cells by a 

 division into a number of small cells which lose their color, and both in posi- 

 tion and structure are very similar to those in the disk-shaped species of Coleo- 

 chsete like C. scutata. Each of these small cells discharges its contents as a small 

 globular spermatium. When one of these comes in contact with the pro- 

 jection from the carpogonium it fuses with it, and the contents pass into the 

 carpogonium, whose contents then divide into a number of cells, carpospores, 

 which closely resemble the non-sexual spores, and like them germinate as soon 

 as they are set free. 



