ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 651 



Bryophyta. 



(By A. Gepp.) 



Branch-formation in Mosses.* — K. von Schoenau has studied the 

 ramification of mosses. He finds that: 1. The resting branch-rndiments 

 can produce shoots which are biologically equivalent to the main axis ; 

 they give rise to innovations. 2. Their development is suppressed until 

 the main axis is prevented from further growth. 3. In regeneration 

 development takes place preferably in the apical rudiments, which there- 

 fore replace the lost apex and produce a false dichotomy. Otherwise 

 the rudiments which develop are those in the best nourished condition. 



4. The most potent factor in the development of lateral axes is light. 



5. Another necessity is damp. G. The form is mostly determined by 

 external influences. 7. The direction of growth is mainly determined 

 by light and damp. Geotropism plays a very small part. 8. Dorsi- 

 ventrality is caused by light, but to some degree is inherited. 9. The 

 position of the lateral axis in relation to the main axis is due to two 

 causes : (a) the position of the rudiment in the basal portion of the 

 leaf-forming segment ; (b) the torsion, either arising during normal 

 growth of the shoot (Fontinalis), or originating in the growing point 

 (Mnium, Sphagnum). 10. There is no sheath, such as Servit has described, 

 at base of the lateral branches. The position of the primary leaves at 

 the base of the branch is due to the mode of growth of the side bud. 

 11. There is no leaf -trace bundle, such as described for all mosses by 

 Bastit, passing from the central cylinder into the branch, except in the 

 branched Polytrichaceffi. 



Sexuality among the Mosses.y — Em. Marchal gives a resume of 

 two sets of new facts ascertained by his father (El. Marchal) and him- 

 self since 1904 during a course of research in the sexuality of the 

 mosses. 1. First, as to the sexualization of the spores. In a dioicous 

 moss, such as Bryum csesjnticium, the spores are, as they have previously 

 shown, half of them male, half of them female — two being male and 

 two female in each tetrad. Each male spore, for instance, produces a 

 protonema which bears only male plants ; and each female spore, female 

 plants only. This is a fact which systematists have not yet grasped. 

 In the dioicous moss the spores and gametophytes are polarized sexually, 

 and only the sporophyte is bisexual. In the monoicous moss, for 

 example Amblystegium serpens, the sexual polarization appears only 

 during the formation of antheridia and archegonia. Incidentally the 

 author notes that Funaria hygrometrica is not dioicous, despite assertions 

 to the contrary. 2. The second question raised is that of the possible 

 intervention of apospory. In the case of the dioicous Bryum csespiticium 

 it is possible to obtain by very careful cultivation from the cell-walls of 

 the unripe capsule a protonema which produces synoicous gametophyte 

 plants. They are, however, sterile — incapable of fertilization. On the 

 other hand, the monoicous Amblystegium serpens readily yields re- 

 generations from its capsule, and the aposporic protonema thus obtained 

 is vigorous and produces normal fertile plants, from which arise 



* Hedwigia, li. (1911) pp. 1-56 (29 figs.). 



t Bull. Soc. Roy. Bot. Belg., xlvii. (1911) pp. 277-85. 



