6 Weiss, Alien Aquatic Pla^its in the Reddish Canal. 



brought about the appearance of Pithophora and the other 



aliens. Its distribution in the Reddish Canal, is more 



restricted than that of Chara Braumi, and much more so 



thdiV\\.\\di\.oi Pithophora. This may of course, be due to 



its more recent introduction, and this view might receive 



some support from the fact that it had not been previously 



observed. But it might easily have escaped notice among 



the Pithophora with which it is mixed, though, when once 



it had been observed, it could be readily picked out 



from the rest of the material. On the other hand the 



fact that it occurs only at the stations 3, 4, 5 and 6, at 



which the temperature was highest during our last visit, 



ranging from 72) to 75°F. is in favour of temperature 



being a limiting factor in the distribution of this alga. 



Wherever it was found, it was pretty abundant, arising 



as small unbranched filaments attached to Pithophora, and 



Chara, and to the leaves of Elodea, Alisma, Potamogeton 



and Vallisneria. Later on the filaments become branched, 



and ultimately the large axial cells become covered in by 



a layer of smaller cortical ones. Some of the latter have 



a denser aspect, and are evidently the sporangial cells. 



The escape of the large non-ciliate monospores, was not 



observed, but empty sporangia were noted, so the plant 



is evidently able to reproduce in the canal by spore 



formation, a fact which is further attested by the numerous 



small plants which have evidently arisen from spores. We 



propose to follow out the life history of this interesting 



alga, and hope that it may help to throw light upon a 



genus of which our knowledge is still very incomplete. 



A comparison of the plant with specimens at the 



British Museum, shows that it agrees very closely, both 



in its macroscopic and microscopic structure with 



Coinpsopogon lepiocladus of Montague,* a species which has 



* Montagne C L. " Cryptoganiia Guyanensis." Ann. des Sci. Nat., 

 Bot., (3), vol. 4. PP- 2S3-309, 1850. 



