LAMINARIALES (HETEROGENERATAE) 177 



The young sporophyte first produces numerous rhizoids of 

 limited growth, but these are later covered by a disk-shaped 

 expansion from which are produced the haptera or crampons. 



Laminariaceae : Saccorhiza {sacco, sack; rhiza, root). Fig. 119. 



S. hulbosa used to be known as Laminaria bulhosa, but for some 

 time it has been removed to a separate genus because it differs 

 from the other species of Laminaria in several important respects. 



Fig. 119. Saccorhiza hulhosa. A, plant ( x ^). B, female gametophyte. C, young 

 sporophyte. D, E, young plants of -S. dermatodea to show origin of bulb. (A, after 

 Tilden; B, C, after Kniep; D, E, after Oltmanns.) 



The persistent lamina arises from a flat compressed stipe with wavy 

 edges which is twisted through 180° near the base as a result of 

 unequal growth, this twisting being regarded as a mechanical 

 device to facilitate swaying. The young sporophyte is attached at 

 first by a small cushion-like disk, but later a warty expansion, the 

 rhizogen^ develops above it and forms a bulbous outgrowth which 

 bends over and attaches itself to the substrate by means of descend- 

 ing crampons. As a result of the development of this adult holdfast 

 the juvenile disk may be lifted completely off the substratum. 



CSA 



12 



