338 SUMMARY OF CURRENT RESEARCHES RELATING TO 



potentially bisexual. And this fact is in perfect harmony with the 

 theory. In the haploid or sexiferous phase the cells of a muss present 

 only one series of chromosomes (one sexual determinant) ; and the 

 unisexual polarity is absolute, and is transmitted without alteration by 

 vegetative propagation. On the other hand, the sporophyte (diploid 

 phase) has, as the result of fertilisation, reunited in its cells two series 

 of chromosomes, including the two sexual determinants. And if we 

 avoid sporogenesis by obtaining direct vegetative reproduction from the 

 wall or stalk of the sporogonium, the resulting gonophytes exhibit by 

 their bisexuality the presence of male and female determinants. Even 

 on the unisexual axes of first aposporic generation the unisexuality is 

 only apparent ; it conceals, as has been shown, a potential hermaphro- 

 ditism ; and the sexual bipolarity, whether it manifests itself or not, 

 impregnates all the cells of the aposporic moss-plant. The Marchals 

 have therefore succeeded in producing out of a strictly dioicous species 

 a new hermaphrodite, or, more precisely, an androgynosynoicous form 

 which is capable of reproducing itself indefinitely as such by vegetative 

 methods. It remains to be determined whether the gametes of this 

 new form could produce an oospore developing into a sporogonium with 

 4 n chromosomes, and what would be the spores of such a capsule. And 

 the Marchals are investigating this problem— a problem of great interest 

 to the systematic bryologist, as explaining, in case of many genera, the 

 existence and meaning of allied species which are almost completely 

 alike in their vegetative characters, and differ in scarcely anything but 

 sexuality. 



Phenomena of Torsion in Mosses.* — W. Lorch has investigated the 

 phenomena of torsion in the stems of Polytrichaceae and of Dicrainiin 

 undulatvm. He describes and figures the apparatus he employed, and 

 gives details of his experiments and results. He finds that the stems 

 of one and the same species may twist to right or left, the direction 

 of the spiral upon which the leaves are set being, in his opinion, due 

 to the direction followed by the successive segments cut off from the 

 apical cell. 



Asexual Multiplication in Blasia and Riella. — H. Buchf gives the 

 results of his experiments on the vegetative reproduction of Blasia 

 piisilla, which confirm and complete the researches of Leitgeb. His very 

 detailed and incompressible resume is reproduced in Hedwigia, xlvii. 

 (1908) Beibl., pp. 74-6. K. Goebel % describes in detail the formation 

 of gemmae in Riella, giving figures of R. Cossoniana, R. Clausonis, and 

 R. Battandieri, and compares the results with those previously recorded 

 for R. Americana by Howe and Underwood. He finds marked analogies 

 with the formation of gemmaa in Marchantia and Lunularia. And he 

 finds other reasons for concluding that the Riellaceae are allied to the 

 Marchantiaceae rather than to the Jungerrnanniaceae, despite certain 

 difficulties. The Marchantiaceae stand at the head of the following four 

 groups : Riccieae, Corsiniaceae, Riellaceae, Marchantiaceae. 



* Ber. Deutsch. Bot. Gesell., xxvi. a. (1908) pp. 78-87 (fig.). 



t Ofv. Finsk. Vet. Soc. Forh., xlix. (1906-7) No. 16, 42 pp. (2 pis.). 



\ Flora, xcviii. (1908) pp. 308-23 (figs.). 



