NOTES AND MEMORANDA. 295 



cess may be reversed occasionally and the contents of the 

 upper part pass down and form a spore below. The order of 

 the formation of the spores is usually basipetal. Quite ex- 

 ceptionally spores may be formed in the rhizoid ; when such 

 takes place the spore is formed not in the upper but in the 

 lower part of the mother-cell. 



Besides spores so formed the author describes another kind 

 of reproductive cells which he denominates " prolific cells." 

 Certain ordinary interstitial (never terminal) joints, without 

 any passing thereinto of chlorophyll, become, simply by ab- 

 sorption and storing up of nutriment, densely packed with 

 chlorophyll-contents and starch-granules. 



The germination of the spore, on becoming free by the 

 dissolution of the adjacent cells, takes place by its pushing 

 out, from each opposite end, a conically-cylindrical process, 

 whereupon it becomes divided, usually about the middle, by 

 a transverse or slightly oblique septum, one of the daughter- 

 cells so formed giving origin to the rhizoVd, the other to the 

 caulo'id ; the transverse wall thus forming a sharp limit be- 

 tween these two parts of the thallus. It would take too 

 much space to try to even condense the author's enlarged 

 details as regards certain exceptional modes of germination, 

 or on the method of ramification. 



As to the germination of the prolific cells set free by dis- 

 solution of the rest of the plant, it takes place in the same 

 manner as the formation of branches from ordinary cauloi'd 

 cells ; that is, the new growth appears as a normal branch 

 just below, that is, a short distance from, the top of the pro- 

 lific cell. 



The plant is most frequently not at all attached, and when 

 it is occasionally so it is not by the rhizoid, but by means 

 of peculiar tendril-like organs developed from the caulo'id 

 (mostly from the terminal cell) called by the author helico'ids. 

 These are common only in one species, rare in others. They 

 are sometimes almost straight, often curved, but most fre- 

 quently quite claw-like and they grasp, like a tendril, around 

 adjoining objects or their own branches. They are densely 

 filled with chlorophyll-contents. 



Looking at the vegetative growth in Pithophoracese their 

 affinity to Cladophorese is apparent. So great is the resem- 

 blance that the author sometimes found no small difficulty in 

 determining whether a sterile specimen really belonged to 

 Cladophora or to Pithophora ; as has been mentioned, the 

 branches in the latter are given ofi" a short distance from 

 the top of the supporting cell and the joints are also habitu- 

 ally very long, but the great distinction is in the (" lap-root-" 



