Hitherto this plant has appeared in British works as a variety 

 of 8. rhizodes, figured at Plate LXX, and notwithstanding its 

 different appearance, when typical specimens of each are under 

 examination, it is not without hesitation that I admit the present 

 to be specifically distinct. Those who are acquainted with the 

 difference in aspect assumed by marine plants, according to the 

 depth of water at which they grow, will best understand my 

 doubts ; remembering that the typical 8. rhizodes grows within 

 tide-marks, and 8. Lyngbycei at a considerable depth, beyond the 

 reach of the tide. And the differences between the two are pre- 

 cisely of the nature of those caused by deep water. If we regard 

 size, we must remember that Asperococcus Turneri in tide pools 

 is seldom more than six inches long ; and that when growing 

 with our 8. Lyngbycei, which it frequently accompanies, it has 

 fronds three or four feet in length and proportionably broad. 

 So also Gracilaria confervoides, which grows to six or seven feet 

 in length in deep water. The distention of the frond in Stilo- 

 phora and the attenuation of the branches likewise increase with 

 depth. On the whole, therefore, the characters typical of our 

 8. Lyngbycei become more strongly marked as the depth of water 

 increases, and appear to me greatly to depend on locality. It is 

 for this reason that I am inclined to question its right to be con- 

 sidered a species, distinct from 8. rhizodes. 



Fig. 1. Stilophora lyngbYjEI ; — part of a frond, the natural size. 2. Segment 

 of a branch. 3. Cross section of the same. 4. Section of a wart. 5. Spore 

 and paranemata, from the same ; — all magnified. 



