— II — 
cells of the sporogonium which is generally still capable of development, can 
give rise to a new plant. In the regeneration of the mosses a new plant is 
not produced directly, but & protonema is first formed from which the plant 
arises, in the same way as the juvenile stage of the plant is developed from 
the germination of the spore.” This is contrasted with the liverworts and 
suggestions are made for further experiment. A few instances of phenom- 
ena of propagation in Bryophyta are cited, such as Marchantia. Dorsiventral 
organs are described and orthotropous and plagiotropous positions are illus- 
trated by Hylocotnium splendens and Mnium undulatum . Anisophylly, or 
the differences in size between upper and lower leaves is illustrated by 
Cycithophorum pennatum and reference is made to Rhacopilum and 
Hypopterygium. Several hepatics are also cited. 
Juvenile froms and stages of development are illustrated in Lejeunia 
Metzgeriopsis, Ephemerum serratum and Funaria hygrometrica, and a 
cushion of protonema of a species of Bryum in Fig. 90 is a remarkable 
instance of an unusually large development of this stage of growth. 
Investigations on the directive influence of light in the polar differentia- 
tion of the spores of many Bryophyta and its influence in the formation of 
roots are still wanting. The question of the influence of light on the position 
of the capsules in mosses still requires experimental investigation. Differ, 
ences are cited between Sphagnum , Orthotrichum and Grimmia and Bux- 
baumia and Diphyscium, Barbula , Catharinea and Bryum . 
The first section of the second volume deals with the sexual organs of 
the Bryophyta with illustrations from Marchantia polymorpha, Phascum 
cuspidatum , Funaria hygrometrica , Catharinea undulata , Monoclea dila- 
tata , Sphaerocarpus, Blyttia. Jungermannia, and Mniuin undulatum. 
The vegetative organs of the Hepaticae, the asexual propagation, the 
phenomena of adaptation in order to retain water and resist drought are 
described and figured in detail as well as the protection of their sexual organs 
and the types of sporogonia and their development, and the germination 
of the spores. 
The life history of various mosses is described from the germination of 
the spore, the development of the protonema, the formation of roots, stems 
and leaves, their special forms and functions, their arrangements for retain- 
ing water, and resisting drought ; their relation to light, the development of 
the sexual organs ; the structure of the sporogonium and its various types 
and adaptations for shedding the spores. 
A few quotations will suffice to show how suggestive of further study 
and experiment these chapters on the Bryophyta are: “ There is wanting in 
the musci the wealth of adaptation in the form of the leaf in relation to the 
retention of water that is so manifest in the Hepaticae : the complex auricles 
are absent. Outgrowths of their surface, such as mamillae or papillae, occur 
in species growing in dry sunny places, such as Hedwigia ciliata , but not 
on hygrophilous species, and would probably disappear if cultivated in 
moisture and shade. The method of sponge construction by means of empty 
cells with perforated walls, is well shown in Sphagnum and Leucobryum ; 
one is fitted to evaporate water rapidly, the other to retain it.” 
