ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
375 
segments. Good instances of the latter are afforded by Tricliocolea tomen- 
tosa and Lophocolea muricata ; and of lamellae on the leaf by Gottschea 
sciurea. Water-sacs occur even in a thallose species, Metzgeria saccata. 
In no case do these receptacles appear to be intended for the capture 
of insects ; their object is simply to render it possible for the surface of 
the plant to be kept constantly moist, without which the majority of 
the epiphytic species could not exist. The water-sacs are especially 
well developed in the genera Lejeunia , Colura , Frullania, and Physiotium ; 
in Colura and Physiotium they are furnished with a movable lid. That 
assimilation takes place in the water-sacs is shown by the fact that the 
air-bubbles which they usually contain increase considerably in size 
under strong illumination. 
Vegetative Organs of Hepatic®.* — Herr G. Ruge has studied the 
structure of the vegetative organs in a large number of Hepatic®. The 
following are the more important results : — 
Cyathodium (Marchantiaceae) presents the simplest case of a sharp 
differentiation between the assimilating and the storing tissue ; the cells 
of the dorsal side contain chlorophyll, those of the ventral side starch. 
In Monoclea Forsteri minute crystals of calcium oxalate were detected, the 
first time this substance has been observed in any of the Muscineae. The 
development of the male and female organs in this species is described 
in detail, the former being now observed for the first time. 
In addition to its occurrence in the frondose Jungermannieae, a dis- 
tinct mid-rib exists also in Dendroceros among the Anthoceroteae. The 
highest development of assimilating tissue occurs in the Ricciaceae and 
Marchantiaceae. In many Hepatic® there is found also a specially 
differentiated mucilage-tissue ; an excretion of mucilage in some form is 
characteristic of all Hepatic® ; the special mucilage-tissue in the thallus 
occurs only in the Anthoceroteae and Marchantiaceae.f That of the 
Anthoceroteae is now described for the first time. Nostoc is very com- 
monly found in the mucilage-cavities, and its parasitism greatly modifies 
their structure. At the base of the female fructification of Monoclea 
Forsteri is a dense tuft of mucilage-hairs. 
The vegetative multiplication of the Hepatic® takes place in a great 
variety of ways. It is effected either by the regeneration of the thallus 
or by means of special organs. Adventitious shoots occur in the 
Jungermanniace®, in Cyathodium , and in Metzgeria. In some tropical 
species tubercles are formed which have not hitherto been described ; 
they appear to be a protection against periodic desiccation. Gemm® 
( Brutknospen ) are not uncommon in the Anthocerote®. 
Stem and Leaves of Physiotium. if — Mr. J. Reeves describes the 
development and structure of the auricles or water-sacs in Physiotium 
giganteum , and the provision for the conduction of water into their cavity. 
The stem of this species presents the remarkable peculiarity that it 
grows by a two-sided apical cell, instead of the three-sided cell hitherto 
supposed to be universal in the acrogenous Jungermannie®. 
* Flora, lxxvii. (1893) pp. 279-312 (1 pi. and 15 figs.). 
t Cf. this Journal, 1884, p. 262. J Journ. of Bot., xxxii. (1894) pp. 33-5 (1 pi.). 
