CURRENT LITERATURE. 95
tissues or cells, as embyro sacs, tapetal cells, pollen tubes, etc. In 1915 Miss Pramkherd drew attention to the frequent occurrence of such cells in differ- ent tissues of young organs of widely different but by no means specialised character. Among ferns they were found in the petiole and sporangioph- ore ; among phanerogams in petiole, hypocotyl, coleoptile, stem, inflorescence axis, plumule bud and pedunole. They tend to occur in regions of activity and rapid elongation, and are due, she supposed, chiefly to amitotic division, and being probably followed by wall-formation, might contribute to the rapid formation of the tissue. Rudolf Beer and Agnes Arber in the paper now under notice, record the occurrence of binucleate and multinucleate cells in vegetative tissues of 177 species representing 60 families, most frequently in the stem but also in roots, and always characteristic of young actively growing tissues. In opposition to the majority of observers they consider that the division of the nucleus has always been a mitotic one, no single instance of direct division having been observed. A peculiarity in the development of the binucleate condition is the formation of what the authors propose to call the Phragmjspherc. After the spindle plate has made its appearance it is apparently resorbed, and the whole phragmoplast with its associated cyto- plasm becomes transformed into a hollow sphere which encloses the two nuolei and ultimately becomes co-extensive with the cytoplasm lining the cell-wall.
The fate of the nuclei varies : in some cases they persist, even, as in the cortex of Rosa, for two years. In some they soon degenerate ; but there is no evidence of fusion.
From the frequency of the occurrence of bi- nucleate and multinucleate cells in growing tissues the authors regard them as a normal feature, a definito phase in the growth of the higher plants.
This phase usually succeeds the meristematic stage and preoeeds the period of maximum growth and may therefore be considered as due to a loss by the cytoplasm of the power to divide, while the nucleus is still capable of doing so. The authors are inclined to think that the diffusion into the cyto- plasm of the nuclear material both at each division (because of the solution of the nuclear-membrane) and on the disintegration of the nuclei, may contri- bute to the cj'toplasm and affect its activities.
P. F. F.
Hepaticae.
Campbell D. H. Studies on some East Indian Hepaticae. Annals of Botany Vol. XXII. No. CXXVII. July 1918.
The writer describes the structure and development of some species of Dumorticra and gives the description of a new monoecious species of the genus from Borneo characterised by the formation of several (5-6) sessile successive male and female receptacles on a series of terminal adventitious shoots. The stucture of Wiesnerella denudata (Mitten) St, is also described. The author concludes that D. velutina. shows the least reduction, for not only are the outlines of the air-chambers quite evident, but the characteristic assimila- tive tissue is present in the form of very numerous superficial papillate cells. In D. trichocephalla, which is more strongly hygrophilous in habit, the reduc- tion of the air-chambers is much more complete, and in a third species, from Hawaii, probably D. hirsuta, the suppression is complete.
