334 Careers : Notes on Yorkshire Bryophytes. 



may reach a length of over 3 cm. I'he capsule-wall consists of 

 two layers of cells, those of the outer layer being- flattened and 

 devoid of fibrous thickenings, whilst the large cells of the inner 

 layer bear incomplete rings or U-shaped fibres, the thickenings 

 being found on the inner and lateral walls and failing on the 

 outer walls of the cells. When the capsule has been carried up 

 by the elongation of the seta the upper half of its wall breaks 

 up into irregular fragments, which become detached, exposing 

 the mass of spores and elaters and leaving the lower half of the 

 Avall as a cup with toothed margins. Each of the dark-brown 

 spores bears on its outer surface a series of ridges which form 

 a network ; the elaters are long and tapering at both ends, and 

 show two or sometimes three spiral fibres. 



So far as the structure of the sporogonium is concerned 

 Pctalophvllum closely resembles Fossombronia, but until Camp- 

 bell's discovery of the Californian plant already referred to, 

 Geothallus tiiberosiis, Petalophylliim was reg'arded as an isolated 

 genus, by reason of the peculiar organisation of the gameto- 

 phyte. Between Petalophylliim Ralfsii and Geothallus there is a 

 remarkably close agreement, so far as the gametophyte is con- 

 cerned. In both cases the shoot consists of a basal cylindrical 

 portion, spreading out anteriorly to form a fan-shaped expansion 

 which carries on either side a series of parallel lamellae (leaves). 

 Moreover, Geothallus is distinguished by the formation of tubers 

 exactly resembling those here described for P. Ralfsii. The 

 two genera differ widely, however, in the organisation of the 

 sporogonium. In Petalophylliim the seta grows out to a 

 considerable length, the cells forming the capsule-wall bear 

 well-developed thickening-fibres, and the spores are accom- 

 panied by long spirally-thickened elaters. In Geothallus the 

 sporogonium is much simpler and resembles that of Sphcero- 

 carpus ; the seta is very short and narrow, the capsule-wall is 

 devoid of fibrous thickenings, and the elaters are represented 

 only by slightly-elongated sterile cells scattered amongst the 

 spores. It is, of course, an open question as to whether much 

 stress should be laid upon the characters of the gametophyte in 

 considering the affinities of these Anacrogynous forms, for not 

 only do tubers occur in several genera of Hepaticae (e.g., Riccia, 

 Fossombronia, Anfhoceros) besides Petalophylhiin and Geothallus, 

 their production being characteristic of xerophytic or sand- 

 inhabiting forms, but Campbell''-' has observed specimens of 

 Sphcerocarpus terrestris which instead of being strictly thalloid, 

 as is usual in this genus, had developed leaf-like appendages 

 somewhat similar to those of GeotJiallus or Petalophylliim. 



*Xotes on SpluFrorarpus, Erylhea, ]\Ia_\' 1S96. 



Naturalist, 



