494 SUMMARY OF CURRENT RESEARCHES RELATING TO 



Bryophyta. 

 (By A. Gepp.) 



Targionia hypophylla.* — Lillian O'Keeffe gives an account of the 

 structure and development of Taryionia hypophylla. She summarizes 

 her results as follows. 1. The thallus of T. hypophylla grows by 

 means of a single apical cell, from which segments are cut off dorsally, 

 ventrally, and on either side. The air-chambers arise by splitting be- 

 tween the epidermal cells, the split extending from the surface inwards 

 through the entire depth of the epidermis ; this process is followed by 

 partial closure of the crack due to turgor of the bounding cells ; the 

 young chamber next undergoes extension, owing to general growth of 

 the thallus tissue, but remains closed for a considerable time, until the 

 divisions occur which cut out the concentric cell-rings around the pore, 

 when the latter opens and continues gradually to increase in area until 

 the general growth of the thallus ceases. The membrane-like rim 

 around the pore of the chamber is formed from the innermost ring of 

 surrounding cells, the cavity of these cells being almost obliterated by 

 thickening of the walls. 2. The antheridial receptacle may be developed^, 

 on special short disk-like branches of limited growth, or on ordinary 

 thallus branches, every intermediate condition being found between the 

 two extremes. The centrifugal arrangement of the antheridia, and the 

 scattered distribution of the ventral scales on the disk-like receptacle, 

 indicate that the latter represents a condensed branch system, in which 

 dichotomy occurs rapidly, and the several growing-points formed are 

 of short-lived activity. 3. The bivalved involucre develops simul- 

 taneously w 7 ith the archegonial group, and represents the peripheral 

 region of the archegonial surface, but its further growth, the formation 

 of interlocking processes on its margin, and its closure until the ex- 

 trusion of the capsule, are dependent on the occurrence of fertiliza- 

 tion in one or more of the archegonia. 4. The young sporogonium 

 does not show the octant stage usually regarded as characteristic of 

 Marchantiales, but approaches the " Jungermannia type," a row of 

 cells being formed by successive transverse divisions before the first 

 longitudinal divisions occur. The spore-mother-cells and the elaters 

 occur in approximately equal numbers, and are irregularly mingled, but 

 there is invariably a layer of elater-forming cells immediately within the 

 single-layered capsule-wall, and these cells may either remain attached 

 by their entire length to the inside of the capsule-wall, or by one end 

 only : in the former case making the wall two-layered in places, in the 

 latter case forming fixed elaters. 



Polytrichacese.f — I. Hagen continues his Notes on the Norwegian 

 moss-flora. In Part xix. he treats of the Polytrichacese. their distri- 

 bution, their history, as well as questions of nomenclature, system, and 

 morphology. Among the morphological points of the family, the author 



* New Phvtologist, xiv. (1915) pp. 105-16 (figs.). 



t K. Norske Vidensk. Selsk. Skr., 1913 (Trondhjem, 1914) No. 1, pp. 1-77. See 

 also Bot. Centralbl., cxxviii. (1915) pp. 194-5. 



