ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 697 



cleavage, and this view has been quoted in all text-books. As regards 

 Marchantiales, however, other views were held by both Hofmeister and 

 Leitgeb. Leitgeb's views on the origin of the stomata of MarchanUa 

 are briefly and clearly given by Vines in the English edition of Sachs's 

 Lehrbuch der Botauik 1882, Appendix p. 1)48, where the stomata are 

 said to " appear originally as depressions in the surface, which arise by 

 definite points (always situate where four cells meet), lagging in growth 

 and so becoming overgrown by the adjacent parts." In 1904 the 

 attention of the authors was attracted to some very young air chambers 

 on a still very small receptacle of a species of Fimhriaria. A cursory 

 examination showed that a re-investigation of the orio^in of the air 

 •chambers was needed, and the authors proceeded to obtain and examine 

 as many of the Marchantiales as were easily obtainable, including species 

 of Riccia, Marchatitia, Lumtlaria, Gonocephalus, Dmnortlera, Fimhriaria, 

 and Plagiochasma. The views of Leitgeb are fully discussed and criticised, 

 and the conclusions of the present authors are stated as follows. The 

 air chambers of Marchantiales arise invariably by the splitting of in- 

 ternal cell walls, usually at the junction of the outermost and first 

 internal layer of cells. Thence, in one type, splitting proceeds outwardly 

 and inwardly more extensively than laterally, and lateral enlargement 

 of the chamber follows by growth ; while in the other type expansion 

 of the chamber is due to extensive inward splitting accompanied by 

 growth. The origin of the air chamber is in all respects like that of 

 intercellular spaces in the vascular plants. 



G-ermiiiatioii and Regeneration of Riella and Sphserocarpus.* — 

 K. Goebel publishes some further remarks on these subjects. He shows 

 that the peculiar wing of Riella is not a subsequent outgrowth from the 

 midrib, but lies in the same plane as the germ-disk and springs directly 

 from it ; and when new shoots are regenerated after injury secondary 

 germ-disks are first produced, and from them arise the new thalline 

 shoots. In Sphccrocarptis the spore produces a germ-tube, which becomes 

 a multicellular cylinder with depressed apex, from one quadrant of which 

 the vegetative point arises, while from two others arise the wings of the 

 thallus. In adventive shoots the same phenomena occur. The forma- 

 tion of sex-organs is remarkably precocious, as Leitgeb has pointed out. 



Regeneration in Mosses.f— J. Westerdijk has experimented on the 

 following mosses with regard to regeneration : Hookeria quadrifaria, 

 Fissidens taxifolius and F. adiantoides, Tortula muralis, Fvnaria hygro- 

 metrica, Dicranella curvata, Ceratodon purpureus, Mnium imdvlatum and 

 M. rostratum, Pohjtrichiim commune, Catluirinea undulata, and Aulacom- 

 nium palustre. He removed portions of the plants from each pole, and 

 as the result he found a growth of rhizoids and protonema took place, 

 principally from the pole itself. Whether rhizoids or protonema arise 

 ■depends on external factors ; darkness and contact with firm bodies 

 inciting the production of rhizoids, while light incites a protonema, 



* Flora, xcvii. (1907) pp. 192-214 (figs.). See also Bot. Gazette, xliv. (1907) 

 p. 72.- 



t Rec. Trav. Bot. Neerlandais, iii. (1907) pp. 1-66. See also Bot. Zeit., Ixv. 

 <1907) pp. 282-3. 



