ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
639 
similar changes to those in the hypocotyl of the embryo of higher plants ; 
the bundle-sheath gradually disappears in the young shoot ; the endoderm 
passes without change ; the pericycle is divided into several layers ; the 
xylem of the diarch bundle is separated from the pericycle by narrow 
phloem-cells ; a large portion of the xylem in the centre of the bundle 
remains unlignified ; and the bundle gradually assumes the concentric 
structure with phloem on each side of the xylem ; later, from this cir- 
cular bundle proceeds one of a horseshoe form, dividing finally into two, 
which present the character of normal stem-bundles. Both primary and 
secondary roots can be transformed into shoots ; and the shoot may then 
either be placed at the end of a root or may spring from it laterally ; in 
the latter case its position shows that it is actually a lateral root, and 
not an adventitious shoot. In Asplenium the root-cap is soon burst and 
thrown off from the apex of the metamorphosed root ; in Platycerium it 
remains attached for a longer period to the apex of the shoot. 
Muscineae. 
Anatomy of the Capsule of Mosses.* — Herr E. Biinger has made a 
detailed examination of the structure of the sporange in a great number 
of mosses, especially as regards the stomates and the assimilating 
tissue. 
The stomates are almost always limited to the lower portion or neck 
of the sporange. While usually bi cellular, as in most flowering plants, 
unicellular stomates occur in Funaria , Physcomitrium, Buxbaumia aphylla , 
Physcomitrella , &c., and three- or four -celled, probably functionless, 
stomates, in the Hypnaceae and Polytrichaceas. In Mnium they are 
depressed below the epiderm from the small size of the guard-cells; 
while in some species, as in Buxbaumia aphylla and species of Ortho • 
trichum, they project above the epiderm and form an external breathing- 
pore. The pore or orifice is generally characterized by its very small 
size, and especially its short length. The fissure or the division- 
wall between the two guard-cells is almost invariably parallel to 
the longer axis of the sporange. The mechanical arrangement for 
opening and closing the stomate is described in detail in a number of 
species. 
The assimilating tissue is least strongly developed in those mosses 
in which the stomates are either altogether wanting, or are functionless 
as in the Sphagnaceae, where the whole of the sporange is composed of 
aquiferous tissue without any air-spaces, and the Andreasaceae, which are 
also destitute of stomates. A variety of intermediate stages are described 
in detail, leading up to the fullest development of the assimilating 
tissue, in the Polytrichaceae. The Cleistocarpae — Archidium, Ephemerum 
Physcomitrella , Phascum , Sphserangium — stand even below Sphagnum in 
the complete suppression of the assimilating and aquiferous tissue • and 
the stomates are also often entirely wanting. 
* Bot. Centralbl., xlii. (1890) pp. 194-9, 225-30, 257-62, 289-96, 321-6, 353-6 
(1 pi.). 
