CONFERVOIDE^;. 



53 



Family 2. Confervoideae. 



The individuals are always multicellular, the cells firmly 

 bound together and united into unbranched or branched filaments, 

 expansions, or masses of cells which grow by intercallary divisions 

 or have apical growth. In the first seven orders the cells are 

 uninuclear, but the cells of the remaining three orders contain 

 several nuclei. Asexual reproduction by zoospores, akinetes or 

 aplanosporos. Sexual reproduction by isogamous or oogamous 

 fertilisation. 



The Confervoidese, through the Ulvaceae, are connected with the Tetra- 

 sporacete, and from the Coleochcctacece, which is the most highly developed 

 order, there are the best reasons for supposing that the Mosses have taken 

 their origin. The Cladophoracece show the nearest approach to the Siplionece. 



Order 1. Ulvaceae. The thallus consists of one or two layers 

 of parenchymatous cells, connected together to form either a flat 

 membrane (Monostroma, Ulva) or a hollow tube (Enteromorpha), 

 and may be either simple, lobed, or branched. Reproduction 

 takes place by detached portions of the thallus ; or asexually by 

 zoospores or akinetes. Gramete- conjugation is known to take 

 place in some members of this order, the zygote germinating 

 without any resting-stage. The majority are found in salt or 

 brackish water. 



Order 2. Ulothricaceae. The thallus consists normally of a 

 simple unbranched filament (sometimes a small expansion con- 



PIG. 52. UlotUrix zonata: a portion of a filament with zoospores, which are formed 

 two in each cell (zoosporangium); the dark spots are the red "eye-spots"; 1, 2, 3, 4, 

 lenote successive stages in the development of the zoospores ; b a single zoospore, v 

 le pulsating vacuole; c portion of a filament with gametes, sixteen are produced in each 

 Kametanginm ; d free gametes, solitary or in the act of conjugation; e the conjugation is 

 completed, and the formed zygote has assumed the resting-stage. 



listing of one layer of cells is formed, as in Schizomeris and 

 Prasiola which were formerly described as separate genera). 

 Asexual reproduction takes place by means of zoospores (with 



