782 SUMMARY OP CURRENT RESEARCHES RELATING TO 



form antheridia ; behind the three leaves which are formed earlier 

 lateral shoots arise, or more often behind the youngest of them only, 

 and always behind the cathodal half of the leaf-forming segment. 

 After the formation of usually only three whorls of leaves, these pass 

 over to the formation of archegonia. In the leaves behind which the 

 shoots arise the formation of a midrib is suppressed, and they are 

 subject also to a variety of displacements in their insertion. The first 

 of the archegonia is formed out of the apical cell, the three or four 

 others out of the youngest segments. When the sexual organs are 

 mature, the female branch projects only slightly above the male 

 inflorescence ; it is only after impregnation that any considerable 

 elongation takes place, by which the male inflorescence is pushed to 

 one side, or comes to stand in the fork, and is then surrounded by 

 two involucral leaves. 



The process is the same in ArcMdium phascoides, only that there 

 is no considerable elongation of the female shoot ; and hence the 

 archegonia and antheridia are apparently inclosed in a common peri- 

 chsetium composed of involucral leaves. 



The same relative position of the sexual organs is exhibited by 

 Pottia subsessilis, P. cavifoUa, P. truncata, P. minutula, P. Heimii, 

 DisticMum inclinatum, Desmatodon ohliqims, D. Laureri, and Oreas 

 Martiana. There is in these cases no doubt that the antheridial 

 receptacle is the termination of the main axis, and that is pushed 

 aside and overgrown by the elongation of the female branch. 



A modification of this arrangement is exhibited by many species, 

 as Ortliotrichum crispulum, O. Hutchinsioe, Bartramia Halleriana, 

 B. pomiformis, Amblyodon dealbatus, &c., where the lateral shoots do 

 not arise immediately beneath the male inflorescence, but in lower 

 whorls of the male shoot. Either these lateral shoots form archegonia 

 at once, or antheridia are again formed through several generations 

 of shoots, archegonia only in a later generation. In Amblyodon these 

 last branches are not always exclusively female, but have often sexual 

 organs of both kinds united in the same inflorescence. The author 

 considers that such a hermaphrodite inflorescence consists of two 

 independent shoots, the female one being formed immediately beneath 

 the antheriditim-bearing segments, without producing any vegetative 

 segments, proceeding directly to the formation of archegonia; this 

 view being confirmed by transitional forms. 



Lesquereux and James's Mosses of North America.* — This book 

 includes all the mosses which are known on the North American 

 continent within the limits of the United States and northwards. 

 900 species are dealt with, a very large portion of them being 

 European. The classification does not ditfer materially from that of 

 Bruch and Schimper (used in Wilson's ' Bryologia '). The definitions 

 of species and genera are commendably full and clear, and the authors 

 have avoided establishing or admitting species upon a slender founda- 

 tion of differential character. 



* Lesquereux, L., and T. James, ' Manual of the Mosse8 of North America,' 

 447 pp.- and 6 pis. 8vo, Boston, 1884. 



