172 



PHAEOPHYCEAE 



lateral rows and there is a long cylindrical stipe which develops 

 abruptly into the frond. 



L. Rodriguezii. The thallus develops annually and splits near the 

 base, the split gradually extending to the apex. Rhizoids develop on 

 the crampons of this species. 



L. saccharina. The margin is thicker than the central part of the 



Fig. ii6. Laminariaceae. A-F, portions of the stipe of Macrocystis passing 

 successively from the epidermis, A, through the medulla, B— E, to the pith, 

 F. h = hypha, v — connecting thread, t = " trumpet " hyphae. G, stages in develop- 

 ment of mucilage canals, L. Cloustoni. H, mucilage canal of L. Cloustoni in 

 transverse section. c = canal, 5 = secretory cells. I, mucilage canal system in 

 L. Cloustoni. c = canal, 5 = secretory cells. (After Oltmanns.) 



thallus and the wavy lamina is produced by continual growth of the 

 central portion without any growth in the marginal areas. The stipe 

 is short and the transition to frond is gradual. 



L. digitata. This possesses a digitate frond that arises by gradual 

 transition from a stipe which tends to be flattened, thus forming a 

 convenient means of distinguishing it from L. Cloustoni. 



Renfrewia. A genus very closely allied to Laminaria but diff"ering 



