332 



are ours also.. Ulota Hutchinsim changes to Weissta Americana 

 (P. Beauv.), Lindb.; U, Liidwigiito Weissia coarctata (P. Beauv.), 

 Lindb.; U. Drtimmofidii, Brid., to W. Drujumondii (Hook, and 

 Grev.), Lindb.; U. B rue hit to JV. ^r/^^//// (Hornsch.), Lindb.; U. 

 phyllantha\.o W.p/ij///anl/ia{Bnd,),l.mdb.; and L^. crista becomes 

 W. ulophylla, Ehrh., and includes U. crisptila as a variety. We 

 rejoice in this combination and think that Mitten's U. AmericaJia 

 should also be included. More prominence is given to general 

 characters than to minute variations of the capsules and peristome, 

 and the result is great clearness and simplicity. E. G. B. 



Aerenchyma: A New Paper on Plant Aeration. — In a recent 

 number of pringsheim is an article by Dr. H. Schenck of Bonn 

 Univ^ersity, entitled ''Aerenchym a tissue of swamp plants homol- 

 ogous with cork in land plants." In this paper are given the 

 results of the study of a large number of swamp plants belong- 

 ing to nine different families, which he examined with respect to 

 the peculiar tissue which he characterizes as Aerenchym. This 

 tissue is pecuhar first in respect to its origin, second its function. 



The author claims that to the various kinds of tissue devel- 

 oped by the phellogen must be added this one. With the excep- 

 tion of the roots of Jiissicea, this tissue comes exclusively from 

 the phellogen layer; in the roots of this genus the original rind 

 cells form a part of it, but these are added to and completed by 

 cells developed from the phellogen. 



As to its function, it is claimed that as this tissue is invariably 

 produced by plants belonging to very different families whenever 

 these plants are subject to certain conditions, it is therefore prob- 

 able that its function is in all cases one and the same. This 

 function, he says, is that of supplying the submerged part of the 

 plant with the necessary oxygen for respiration. It is held by 

 certain other botanists that in a number of these plants the tissue 

 performs the office of swimming organs. 



In answer to this, he says the "aerotropische" roots of Jii^st(^^ 

 Peruviana cannot be considered as swimmincf organs, and that 



S ^*£3 



those free swimming plants related to this may have inherited the 

 tendency to produce this tissue, although at present no longer 

 requiring it for breathing purposes. These roots he describes as 

 a second form, springing from the submerged stem, and growing 



