68 SL.M.MARY OF CUBRENT EESEAECHKS RELATING TO 



Bryophyta. 



Early Stages in the Development of the Sporophyte of 

 Sphagnum subsecundum. — Geo. S. Bryan {American Journal of 

 Botany^ 11)20, 7, 296-o0o). The young sporophytes were dissected out 

 of the archegonium, and the following summaiy is given : — 1. The 

 fertilized ^^g di\ides by a horizontal wall into two approximately equal 

 cells. A filament of cells — six or seven in number— is usually formed 

 before longitudinal divisions occur. 2. In the material studied the 

 first transverse wall cannot be traced with certainty in the older stages ; 

 licnce no exact statement can be made as to the contribution of each of 

 these two cells in the development of the sporophyte. 3. It is reasonably 

 certain that apical growth occurs, 4. The Ijasal portion of the young 

 sporophyte may have walls appearing in a regular or in an irregular 

 order. As a result of the former process there is developed a long, 

 slender type of young sporophyte ; as a result of the latter, a shorter, 

 bulbous type. 5, The number of primary segments, i.e. segments formed 

 bv walls transverse to the axis of the archegonium, has not been found to 

 exceed twelve. G. A considerable number of very young sporophytes 

 show basipetal disintegration. In conclusion, the early embryogeny of 

 Sphagnum is nearer to that of the Jungermanniales than to that of 

 Anthocerotales, though the endothecial origin of the sporogenous tissue 

 in Sphagnales and Anthocerotales has been much insisted on as evidence 

 of affinity. A. Gepp. 



Segmentation of the Apical Cell and Position of the Leaves in 

 Mosses.— E. M. Mekl {Flora, l'J17, 109, 189-212, 13 figs. : see also 

 Bot. CentraJhl., 1918, 138, 25-6). In the twenty-seven species examined 

 the majority showed the position of the youngest septum of the apical 

 cell to be in an a-nodal direction. Marked exceptions are Barhula 

 palndosa (in part) and Fontinalis (always). A principal argument 

 against Seckt's assumption of the original " parallel " arrangement of 

 the inner to the outer edge of the youngest segments is that in most of 

 the mosses examined the inner edge actually intersects the other ; and 

 further, that this mode of division occurs in many mosses together 

 with the recognized course of segmentation, which, however, encroached 

 somewhat in an a-nodal direction. No definite connexion was found 

 between the different stages of the encroachment of the wall and the 

 relationship and position of the species. In the case of species showing 

 both kinds of segmentation the type in which the inner edge does not 

 intersect with the outer is confined to the more tender shoots. The 

 youngest septum is already inclining in an a-nodal direction. The form 

 of the septum which divides the apical cell from the youngest segment 

 is not an even surface, but appears much crumpled and twisted awry. It 

 is precisely this peculiariiy of the segment edges which lends to the 

 apical cell its usttal pecuharly twisted form. Crumpling of the septa 

 occurs also in mosses in transveise walls of rhizoids grown in the dark. 

 The encroachment in an a-nodal direction in any segmentation layer and 

 the whole form, so peculiarly twisted, of the segments play a large part 

 in the leaf arrangement of mosses. The amount of the torsion would be 

 probably governed by the same factors as in the spirotrophic growth of 



