14 Tans ley and Chick. — Notes on the 
experiment. Subsequent observers have added comparatively 
little to our knowledge of the histology of the stem of the 
moss-gametophyte. The most important papers are Bastit’s 
Recherches anatomiques et physiologiques sur la tige et la 
feuille des Mousses (Rev. Gen. de Bot., tome iii, 1891), and 
a contribution by Coesfeld (Bot. Zeit., 1892) bearing exactly 
the same title^as Haberlandt’s classical work. The former con- 
tains descriptions of the anatomy of the aerial stem, foliage- 
leaves, rhizome, and scales of Polytrichum juniperinum, but 
while Bastit pays more attention than Haberlandt to the 
structure of the Polytrichaceous rhizome, and describes some 
important new features, he fails to connect his descriptions 
with Haberlandt’s careful and thorough account of the minute 
histology of the aerial stem, with the result that our know- 
ledge of this part of the subject is left in a vague and 
unsatisfactory state. 
A reinvestigation of several species of Polytrichum with 
the object of getting a clear idea of the histology of the stem 
as a whole, has led to the discovery that the structure of the 
rhizome is considerably more complex than Bastit apparently 
suspected, the tissue-systems corresponding in many points 
with those that Haberlandt has described for the aerial stem. 
Haberlandt and Bastit both described Polytrichum juni- 
perinum, and the latter mentions that the other species are 
fundamentally similar. This is true in broad outline, but 
P. commune possesses distinctly better characterized and 
more highly differentiated tissue-systems than P. juniper inum, 
P. formosum, and P. piliferum> the other species we have 
investigated. For this reason it will be most convenient to 
describe pretty fully the features it presents, afterwards re- 
ferring to the points of difference exhibited by the other 
species. Haberlandt (op. cit, pp. 366, 368) drew attention to the- 
fact that in relation to the stereom, the rhizome of Poly- 
trichaceae has a distinctly root-like structure. As a matter of 
fact, the resemblance to the root of a vascular plant extends 
in a most striking way to nearly all the tissue-systems. 
Cortex. The rhizome, which may be roughly circular in 
