179
CURRENT LITERATURE.
Distribution
Becari, O., The Palms of the Philipine Islands, Philippine Jour- nal of Science XIV No. 3, {March 1910) pp. 295-362, 3PI.
The author gives a list of the palms of these islands with notes on points of special interest, and descriptions of new species ; and prefaces it with a general survey. The number of species at present known is 120, of which about 20 are non-endemic and for the most part belong to the littoral swamps of neighbouring countries. Nearly all the endemic species belong to Malayan genera. The great bulk of the palm flora belong to the genera Piuanga, Areca, Calamus and Dccmero^s. Of the 36 known species of Areca no fewer than 10 are characteristically Philippine ones, and from the occurrance here of closely allied species, and their absence elsewhere, the author considers that Areca catechu acquired its specific characters in these
islands.
P. F. F.
Evolution
Arber, Agnes, The Law of Loss in Evolution — a paper read before the Linnaean Society No. 7th, 1918 and, abstracted, in Proc. Linn. Soc. Lond. Oct. 1919. pp. 70-78.
Mrs. Arber in this paper formulates under the name of the' Law of Loss' a principle which appears to have operated in the evolution of plants. By this she means the general rule that " a structure or orgen once lost in the course of phylogeny can never be regained ; if the organism subsequently has occasion to replace it, it cannot be reproduced, but must be constructed afresh in some different mode." As instances of the working of this Law of Loss, though in the nature of things formal proof cannot be given, she points out that certain water-plants, Ceratuphi/llum and Ltricularia sp., are entirely rootless even as seedlings, and since the evidence is all in favour of a terres. trial origin of the Flowering Plants we are driven to the conclusion that these plants have lost the power of producing roots, and that in both the need of an absorbing organ has reasserted itself and has been met, not by the re- establishment of true roots, but by the development of special subterranean shoots which act as roots. Again it seems probable that the Monocoty ledons, derived, as we have good reason now for believing, from a dicotyledonous ancestor, have lost the property of forming a true leaf-lamina, so that their leaves consist of base and stalk, or eyen leaf-base alone ; when an attemt is made to produce a compound leaf, it isiby a totally different method. As another instance she points out that Flowering Plants are considered to have been derived ultimately from a fern-stock in which the male gamete» in harmony with its aquatic life, is ciliated ; but the submerged flowers of present-day phanerogams have merely slightly modified pollen grains which are dependent on currents in the water to find the ovules, the art of producing cilia havingbeen lost. Other instances are the pappus scales of certain Compositte which there is good reason to believe are hairs, not modified sepals, aiuL'Small has given reasons for supposing that this order was derived
