CYCLOSPOREJ!. 73 



Family 2. Cyclosporeae. 



The individuals are rnulticellular, with growth by an apical 

 cell. The thallus often bilateral is differentiated into a root- 

 like structure (attachment-disc), and stem, sometimes also into 

 leaves (Sargassum). Sometimes a differentiation occurs into 

 various tissue-systems, viz. an external assimilating tissue, a storing 

 tissue, a mechanical tissue of thickened, longitudinal, parenchyma- 

 tous, strengthening cells, and a conducting tissue of sieve-cells, or of 

 short sieve-tubes with perforated walls. Colouring material, as 

 in Phaeosporege. Vegetative reproduction can only take place by 

 means of detached portions of the thallus (Sarg>issum\ which are 

 kept floating by means of bladders (Fig. 70 A, a, Fig. 72). Zoo- 

 spores are wanting. 



The sexual reproduction takes place by oogamous fertilisation. 

 The oogonia and antheridia are formed inside special organs 

 (conceptacles), and are surrounded by paraphyses. The concep- 

 tacles (Fig. 70 JJ, Fig. 71 b) are small, pear-shaped or spherical 

 depressions, produced by a special ingrowth of the surface cells 

 of the thallus, and their mouths (ostioles) project like small warts ; 

 they are either situated near the end of the ordinary branches of 

 the thallus (Fucus serratus, Fig. 71 a) which may be swollen on 

 this account (Fucus vesiculosus, Fig. 70 A, 6), or on special short 

 branches (AscopTvyllum, Sargassum). The vertical section of a 

 coiiceptacle is seen in Fig. 70 B (see also Fig. 71 &) where, in 

 addition to the paraphyses, oogonia only are seen (F. vesiculosus is 

 dioecious male plant, yellow-brown; female plant, olive-brown); 

 but in some species antheridia, together with oogonia, are pro- 

 duced in the same coiiceptacle. The oogonia are large, almost 

 spherical cells, situated on a short stalk, in each of which are 

 formed from 1-8 (in Fucus, 8; in Ascophyllum, 4; in Halidrys, 1 ; 

 in Pelvetia, 2) rounded, immotile oospheres. The wall of the 

 oogonium ruptures, and the oospheres, still enclosed in the inner 

 membrane, are ejected through the mouth of the conceptacle, and 

 float about in the water, being finally set free by the bursting of the 

 inner membrane. The antheridia are oblong cells (Fig. 70 G, a), 

 many of which are produced on the same branched antheridio- 

 phore (Fig. 70 C) ; the numerous spermatozoids are provided 

 with 2 cilia and are very small (Fig. 70 D, two antheridia sur- 

 rounded by spermatozoids, one being open). The spermatozoids, 

 still enclosed by the inner membrane of the antheridium, are 



