Beiträge zur Biologie der Pflanzen

Abstract

THE third part of Cohn's “Beitrage,” now before us, completes the first volume, and let us express the hope that we may have another volume before very long. Curiously, each of the three parts has been separately paged, an arrangement which renders it necessary to note the part as well as the page when the index is consulted. If we may judge from the size and price, each part has increased in importance, so that the third part has more papers and is nearly double the size of the first. In all the parts there have been papers of great interest and value, and those in the present part are in no way behind their predecessors. Dr. Cohn himself contributes three papers to the present part, Dr. J. Schrœter two, while Drs. L. Just, A. B. Frank, Richard Sadebeck, and Eduard Eidam, each one. The first paper is by Dr. Schrœter on the Development of certain Rust-Fungi. On Carex hirta, one of the Uredineæ was observed which Dr. Schrœter believes to be Puccinia caricis of De Candolle; and as he had reason to suspect that Æcidium urticæ of Schum was only a stage in the life history of P. caricis, experiments were made to ascertain definitely whether P. caricis was heterœcious, and if so, whether Æcidium urticæ was one of the stages. Details of the experiment are given, and Schrœter concludes that Æcidium urtica is a stage of Puccinia caricis. In a note to his paper, Dr Schrœter mentions that Dr. Magnus, of Berlin, has made similar experiments with the same result, an important confirmation of the remarkable habit these curious plants have of changing from one host to another, and at the same time changing the form of their spores, a condition describee by De Bary long ago in the rust of wheat. A second form noticed by our author is a species of rust common on many grasses. It has many names, and Dr. Schrœter calls it Uromyces dactylidis, Ottli, (Uromyces graminis, Cooke). One stage is spent in our common grasses, such as Dactylis glomerata, Poa nemoralis, P. trivialis, P. annna, P. pratensis, &c. The other stage occurs on Ranunculus bulbosus, R. repens, and R. polyanthemos, and is known as Æcidium Ranunculacearum, D.C. The Æcidia occurring in other Ranunculaceæ (Clematis, Thalictrum, &c.) seem to belong to other species. Dr.L. Just's paper is a physiological one, showing the effect of the epidermis of the apple in preventing loss of water by transpiration. The third paper, by Dr. J. Schrœter, on the effect of disinfectants in lower organisms, shows markedly the value of carbolic acid in destroying germs. In the fourth paper Dr. A. B. Frank shows how light influences the relative time of development of the flowers in a catkin, those flowers opening first which receive the most light. Next follow two papers by Dr. Ferdinand Cohn, one on the “Function of the Bladders of Aldrovanda and Utricularia,” the other on the “Development of the genus Volvox.” English readers are already acquainted with the more important facts recorded in the first paper, as they have already been made use of by Mr. Darwin in his work on “Insectivorous Plants.” The second paper is of especial interest in relation to the re-distribution of the Thallophytes, by Prof. Sachs, in the fourth edition of his justly celebrated “Lehrbuch.” The structure of volvox is carefully described, and its modes of reproduction both sexual and non-sexual. The non-sexual reproductive cells Cohn calls Parthenogonidia. Non-sexual reproduction seems to take place during the whole year, and the alternation of generations is completed by the occurrence of sexual reproduction in the spring. The volvox-colony, or cænobium, is either monœcious or diœcious, the female cells, or Gynogonidia are either produced along with the male cells, or Androgonidia, in the same colony, or they are not. Cohn proposes to divide the Linnæan Volvox globator into two sub-species, namely, (a) Volvox monoicus, and (b) Volvox dioicus, the former having both andro- and gynogonidia, the latter either one or other. The structure of Volvox is very like that of Pandorina, but the reproduction is like that of Sphaeroplea, and it belongs, not to the Zygosporeæ, which have conjugating zoospores, but to the Oosporeæ. Cohn, however, does not consider the Zygosporeæ and Oosporeæ to be separate classes of the Thallophyta, but only to be subdivisions of one class, to which he gives the name of Gamosporeæ. The next division Cohn calls the Gamocarpeæ, a division quite equivalent to Sachs' Carposporeæ. In the Gamocarpeæ there are two methods of fertilisation. One by means of the Pollinodium, analogous to the conjugation in the Gamosporeæ, the other by Spermatia, resembling the Spermatozoids. In the higher plants a somewhat similar arrangement exists; the Muscineæ and Vascular Cryptogams having Spermatozoids, while the flowering plants have pollen and pollen-tubes, showing a certain analogy to the pollinodium of some of the Carposporeæ.

Beiträge zur Biologie der Pflanzen.

Herausgegeben von Dr. Ferdinand Cohn. (Breslau, 1875.) Drittes Heft.