932 RECORD OF CURRENT RESEARCHES RELATING TO 



Algae. 



Formation of the Siphons and Tetraspores in Polysiphonia.*— 

 Professor Wright considers the frond of Polysiphonia as not, correctly 

 speaking, articulated or jointed. As regards the development of the 

 central tube, in the living state there is no central cavity in the 

 frond ; but there is a central cell many times longer than broad, 

 putting one in mind of a prosenchymatous cell, with four or more rays 

 proceeding from about its central portion, and its two poles somewhat 

 dravpn out. In the early disk-shaped condition of the frond a division 

 takes place, apparently simultaneously, into a central cell, and four 

 others surrounding it in the form of a cross, the central cell being the 

 smallest. As development progresses, the central cell or tube grows 

 only in length, or, at least, very little in breadth ; while the four sur- 

 rounding cells grow both in length, width, and depth, forming 

 ultimately what are known as the " siphons." The evolution of the 

 tetraspores is very much the same as in Griffithsia. 



Fertilization of Red Algse by the Agency of Infusoria.f — Pro- 

 fessor Dodel-Port, of Zurich, has communicated to ' Kosmos ' an 

 account of some exceedingly interesting observations made by him on 

 the fertilization of a Floridean alga, Polysiphonia siihulata T. Ag., 

 which appears from his researches to present a singular combination 

 of analogies with the auemoj^hilous and eutomophilous phanerogamous 

 plants. An abstract of Professor Dodel-Port's paper, with figures, 

 appears in ' Nature.';}: 



Like many other Floridean, Polysiphonia siihulata is dioecious, and 

 the male and female plants appear often to grow at a considerable 

 distance apart. The antherozdids, which are produced from anthe- 

 ridia presenting a considerable external resemblance to microscopic 

 ears of maize, are described as mere globules of protoplasm, con- 

 taining a small, highly refractive nodule and a few plasma granules, 

 but entirely destitute of cell-wall, and of the cilia by means of which 

 the antherozoids of so many algre make their way through the water 

 in search of the female organs which they are destined to fertilize. 

 The antherozoid is thus precisely analogous to the pollen-grain of an 

 anemophilous phanerogamous plant. 



The female reproductive organ in this plant is a multicellular body 

 forming an outgrowth from the apical parts of the branches of the 

 thallus. The youngest of these carpogonia is found nearest the apex, 

 those lower down being more mature. The structure of the carpo- 

 gonium is described by Professor Dodel-Port in detail, but the most 

 important point for our present purpose is the presence at its summit 

 of two hair-like organs — a forked hair composed of several cells, and 

 a trichogyne, a slender, colourless, unicellular hair, a little shorter than 

 the forked hair, and i)roduced from the surface of the carpogonium at 

 a later period, making its appearance, in fact, about the time when the 

 unfertilized carpogonium arrives at maturity. When full grown, it 



* 'Trans. Irish Acad.,' xxvi. (1879) p. 47. 



t 'Kosmos,' 1879 ; see ' Pop. Sci. Rev.,' iii. (1872) p. 421. 



j ' Nature,' xx. (1879) p. 463. 



