26 



SCIENCE. 



[N. S. Vol. XI. No. 262. 



This extensive and very detailed work brings 

 together a large number of observations on the 

 vegetative reproduction of the true mosses by 

 means of cuttings and of gemmae, by vehich are 

 meant those structures which serve, like the 

 spores, to disseminate the plant over more or 

 less extended distances. Interesting matters of 

 biological interest are suggested to the mind by 

 the analogies existing between these organs and 

 seeds, but these will be referred to later on in 

 the review. 



The text is divided into two parts. A first or 

 special part consists of a descriptive treatment 

 of gemmae and cuttings and of their behavior, 

 arranged along taxonomic lines. The general 

 part which follows treats of the morphological 

 and anatomical structure of the organs under 

 consideration, of their germination and of the 

 conditions necessary for their occurrence and 

 growth. 



The large number of observations brought 

 together in the special part prevent any ade- 

 quate presentation in the limits of a review, so 

 that it is possible only to point out that the 

 great variety of asexual reproductive bodies 

 which are found in the mosses may be reduced 

 to a few types, viz.: the stem, leaf and pro- 

 tonema types. The stem type is found in those 

 plants in which the stem is transversely break- 

 able at intervals throughout its length, or merely 

 at its base or apex. In this type the leaves may 

 be reduced, resulting in bulbil formation, or the 

 stem, to form brood-buds. 



The leaf type occurs in forms in which the 

 leaf is broken off as a whole and germinates, or 

 is separable into fragments, each acting simi- 

 larly. 



True brood-bodies, so called by the author, 

 arise only from the protonema in the wide 

 sense, including that produced from the stem 

 (rhizoids) and the chloronema. 



The facts in this part which will interest espe- 

 cially, perhaps, the general botanist, are those 

 relating to the methods by which these brood- 

 organs are separated from the parent plant. 

 This separation is accomplished either by the 

 tearing of certains cells (rhexolytic) or by a 

 splitting apart of cells by the behavior of the 

 inner lamella (schizolytic). The rhexolytic 

 process may be provided for by a special zone 



of cells or by, a single cell, according to the com- 

 plexity of the structure. The cell appointed 

 for the sacrifice is called by Professor Correns a 

 ' tmema ' a term which constitutes a very pic- 

 turesque addition to botanical terminology, the 

 more so when one contemplates its com- 

 pounds ' dolichotmema,' ' brachytmema ' and 

 the hybrid 'strecktmema.' 



In the special part are first discussed the mor- 

 phology and phylogeny of the brood-organs. 

 Here the author advances the notion that the 

 aerial part of the moss plant {i. e., the stem and 

 leaf) is phylogenetically older than the pro- 

 tonema and that it results from a reduction of 

 the moss stem, though not, says the author, in 

 the sense of Sachs and others, according to 

 whom the oblique position of the transverse 

 walls of the protonema is an indication that its 

 terminal cell is the homologue of the apical cell 

 of the moss stem, an explanation which, it will 

 be conceded quite generally, is forced. Accord- 

 ing to the author's view, the forms such as 

 Ephemermn and Buxbaumia are reduced and not 

 primitive as to their shoot characters. This 

 statement is probably correct in itself with re- 

 gard to Buxbaumia, high authority to the con- 

 trary notwithstanding ; though it is diflBcult to 

 see why this fact may not very naturally and 

 easily harmonize with the opinion of Goebel by 

 supposing that a secondary reduction, correlated 

 perhaps with the more pronounced develop- 

 ment of the sporogonium, has taken place. 

 This position is strengthened by the indubitable 

 fact that analogous reduction has taken place in 

 the sporophyte of some of the Spermatophyta. 



Following is a discussion of the structure and 

 development of brood-organs. A circle of in- 

 terest centers in the paragraph in which it is 

 pointed out that the nematogonal cells (the in- 

 itial cells which give rise to protonemal struc- 

 tures) preserve their embryonic peculiarities, 

 and regards this as an especially good example 

 of the 'continuity of the germ plasm.' 



The special adaptations for the abscission of 

 brood-organs have already been referred to. It 

 may be added that active loosening of the brood- 

 bodies is of very restricted occurrence. In the 

 vast majority of cases the breaking away is 

 passive, depending on the impact of air, water 

 and animals. The same end is held by some 



