i8o 



« 

 1 



THE ALGAE 



pansion. In older plants this disc is replaced by the haptera or 

 crampons which arise as papillate outgrowths from the stipe. 



Laminariaceae : Saccorhiza (sacco, sack; rhiza, root). Fig. loi 



vS. polyschides used to be known as Laminaria bulbosa, 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. 

 The persistent lamina arises from a flat compressed stipe with 

 wavy edges which is twisted through i8o° 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 disc, 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 des- 

 cending crampons. As a result of the development of this adult 

 holdfast the juvenile disc may be lifted completely off the sub- 



Fig, loi Saccorhiza polyschides. A, plant ( x ^). B, female game- 

 tophyte. C, young sporophyte. D, E, young plants of 6". dermatodea 

 to show origin of bulb. (A, after Tilden; B, C, after Kniepi D, E, 



after Oltmanns.) 



