9° The Ohio Naturalist. [Vol. VII, No. 5, 



the plicae are the last portions to be eroded away and hence thev 

 frequently stand out as long actmiinations beyond the blade 

 proper. The stipe is exceedingly short for so large a plant, sel- 

 dom if ever exceeding 5 cm. The holdfast has no hapteres rising 

 from the stipe but instead consists simply of the primitive disc, 

 which becomes about 3 cm. in diameter covering thus a verv 

 much smaller area than the holdfast of those kelps which have 

 a nuinber of hapteres to increase the strength of their hold on the 

 rocks. As in Renfrewia the surface of the primitive disc (not 

 the stipe above) is subject to local secondary growth by which 

 means branches are formed which pass outward and strengthen 

 the holdfast. These are, however, so flat and so closelv ap- 

 pressed to the disc that they are not noticeable except in sections, 

 (See figure of Renfrewia, Postelsia 1906: Fl. 18.) 



Specimens in fruit are not easy to find at Port Renfrew dur- 

 ing the summer season. Late in the season, however, in old 

 plants may be found at the base of the lamina on both sides, 

 the lanceolate fruiting patches. Froximially they may extend 

 to within a millimeter of the base of the lamiina following its 

 margin around till its full width is attained at which point they 

 suddenly narrow to the plicae up which they extend for a dis- 

 tance of about 25 cm., making the w^hole sorus 40-50 cm. long. 

 At its tip the fructiferous area extends much further up in the 

 grooves than on the ridges of the plicae, thus forming on one 

 side three and on the other two or four acuminate points 5-25 

 cm. long. 



It will be of interest to compare the positions of the .sori in 

 Cymathere and such kelps as Nereocystis. In the latter the 

 gonidia are born out near the tips of the branches perhaps a 

 hundred feet from the attachment of the holdfast. Instead of 

 maturing in one definite short season as seems most likely to be 

 the case with Cvmathere, thev are borne continuously from the 

 time the plant becomes m.ature till it is torn up by the waves. 

 When liberated the zoospores must be carried long distances by 

 the waves, in addition to the space they traverse by their own 

 activity, before thev settle down to the substratum. But in 

 Cymathere, growing in relati\cly quiet water, they are set free 

 within a few inches of the station of the parent plant and might 

 be expected to settle close around it. The habit of the one would 

 be most favorable for wide dispersal but only a very small pro- 

 portion of the repi'oductive bodies would succeed in establishing 

 themseh'es in favorable situations. The other would be slower 

 in dispersing itself but a larger percentage of the spores would 

 start favorably. These inferences are well borne out by the 

 facts of the distribution of the \-oung of the two species. Nereo- 

 cystis, it will be recalled, thrives only in the deep water ofi" sliore 

 where it is able to reach the surface with its long stipe. But on 



