269 



The author regards the Musci as neither agaraous nor cryploga- 

 nious, but as the highest order of acotyledons, " forming the next link 

 to monocotyledons," and as taking " precedence of the Filices, Ly- 

 copodia and Equiseta, in which inflorescence is unknown." He 

 thus defines the Musci : — 



" Plants with stems bearing horizontal leaves, which are mostly 

 composed of one layer of cells, and furnished with 

 thickened nerves. Inflorescence surrounded by proper 

 involucral leaves. Male flowers composed of anthers, 

 antheridia ; female, of pistils, archegonia, which, as 

 well as the antheridia, are mixed with slender threads, 

 paraphyses. Fruit an unilocular capsule, bursting at 

 the sides or operculate, surmounted by a calyptra." 



After explaining the inflorescence, and especially the character of 

 the capsule, as either being without a regular opening and bursting at 

 the sides (astomate), or furnished with an operculum, which, being 

 removed, leaves the capsule closed by a membrane (stomate), and 

 also the mouth of the capsule as naked (gymnostomate), with hygro- 

 scopic teeth (peristomate), or with the sporular sac also divided above 

 into processes and cilia (diploperistomate) ; he goes on to observe 

 that " in some well-marked genera, as Encalypta, Orthotrichum and 

 Zygodon, there exist gymnostomate, peristomate and diploperistomate 

 species, too closely allied in all other respects to be separated gene- 

 rically in any natural arrangement. In Weissia, including as of one 

 genus, Astomum Mittenii, Phascum crispum, P. rostellatum, and all 

 the Hyraenostoma, Gymnostoma, and Weissiae of 'Bryologia Europsea,' 

 are seen species astomate, stomate, gymnostomate and peristomate ; 

 and most of these mosses without the presence of fruit would be dif- 

 ficult enough to distinguish as species, to say nothing of genera; — 

 from which the conclusion seems evident, that as a more or less per- 

 fect series of progressive developments from astomate to diploperi- 

 stomate capsules may occur in a single genus, so any degree of 

 development less perfect than the diploperistomate rriay be considered 

 but an imperfect state of that degree, and of no importance in generic 

 distinctions whenever it is possible to trace a higher." 



In the arrangement founded on these views, M. C. Miiller's plan of 

 dividing the genera into groups by the form of the cells of the leaves 

 is adopted with some modifications. Tlie following is a skeleton of 

 the arrangement: — 



