182 
NEW BRITISH MOSS. 
sumed, it seems natural that a flow of sap should set in in the 
direction of that part. This includes circulation and the 
formation of vessels. But, as regards the latter process, two 
questions arise. Is a vessel a distinct formation ? or is it a 
number of cells which have coalesced (their partitions being 
removed) to form a vessel? The second method seems to he 
the more probable way. The contents of one cell would 
burst through its walls at the weakest point and enter the 
next cell, and this process would be continued till, at length, 
it resulted in the formation of the vessel. These are the 
more important subjects involved in the consideration of the 
inner tissues of the plant. In Chapter V. the “Physiological 
Integration of Plants” is dealt with, and we And that an 
increase of differentiation implies a corresponding increase of 
integration. In the lower forms of plant life there is little 
integration observable, but as higher forms are studied and 
physiological division of labour takes place, then integration 
is the accompaniment. “ Always the gain of power to dis¬ 
charge a special function involves a loss of power to perform 
other functions,” and, therefore, integration must take place 
in order to keep pace with differentiation. 
“ Thus, that which the general doctrine of Evolution leads 
us to anticipate, we find implied by facts. The physiological 
division of labour, among parts, can go on only in proportion 
to the mutual dependence of parts ; and the mutual depen¬ 
dence of parts can progress only as fast as there arise 
structures by which the parts are efficiently combined, and 
the mutual utilisation of their actions made easy.” 
NEW BBITISH MOSS. 
I am pleased to report that Dicranum undulatum, Ehrliart, 
was found, for the first time as a British plant, near Great 
Wolford, Warwickshire, May 31st of this year. This I picked 
up whilst hurrying to catch a train, and as I did not recog¬ 
nise it until I reached home, I was unable to form an opinion 
as to whether it was abundant or otherwise. At the end of 
last week, however, I paid another visit to the locality, and 
found that the tropical heat of the last week or so had so 
shrivelled up the mosses that I had some difficulty in again 
finding my plant; but so far as a two hours’ search would 
reveal, I think it must be recorded as very sparse in 
quantity. Possibly in the autumn and spring months of the 
year it may have been more abundant. Having unearthed 
it in this locality, I have great hopes of being able to find it 
