212 THE ALGAE 



to that region. At one time it was thought that plants of S. natans, 

 together with one or two other species that behave similarly, were 

 attached in the early stages, but there would now seem to be good 

 evidence that they remain floating throughout the whole of their 

 life cycle. Borgesen suggests that these perennial pelagic species 

 originally arose from attached forms such as 5. vulgare, S. filipen- 

 dula and S. hystrix. 



Sargassaceae : Carpophyllum (carpo, frmt; phy Hum, leaf). Fig. 119 

 This genus, confined to south temperate oceans, consists of a 

 number of species. The plants are bushy and from the main axis 

 arise pinnately a number of leafy appendages. The fertile recep- 

 tacles arise later in the axils of these leafy appendages though in at 

 least one species the subtending leaf is absent. The plants grow at 

 or below low water-mark and are highly compressed with no 

 gelatinization of the internal tissue. Most of the tissue consists of 

 meristoderm and cortex with Httle or no medulla. 



Anomalae 

 HORMOSIRACEAE : Hormosira (hormo necklace; sira chain). Fig. 120 

 The sporophyte, which has the appearance of a bead necklace, 

 is composed of a chain of swollen vesicles (internodes) connected 

 by narrow connectives (nodes). Growi±i takes place by means of a 

 group of four apical cells, and these give off branches alternately in 

 a dichotomous manner, the branches usually arising at the inter- 

 nodes, but apart from the discoid holdfast, there is no differentia- 

 tion into appendages comparable to those of the other Fucaceae. 

 The basal intemode is soHd but all the remainder are hollow: the 

 nodes are also soHd because they are composed solely of epidermis 

 and cortex. The sporoph>l:es are dioecious, the conceptacles being 

 borne on the periphery of the inflated nodes. Although eight ova 

 are originally formed in the oogonium only four attain to maturity, 

 but in this genus, however, it is a case of degeneration of eggs 

 and not merely of nuclei. When the ova are released from the 

 oogonium they are still surrounded by the endochiton. This soon 

 ruptures and releases the mature ova. After fertilization has taken 

 place a special fertilization membrane is produced, which is com- 

 posed of two layers, the inner one being of cellulose. Another 

 interesting feature of this genus is its capacity to form and shed a 



