ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 93 



merismatic portions of the growing point at right angles to the longer 

 axis of the gemma. 



Attempts to produce similar gemmae in Preissia commutata and 

 Beboulia hemisphserica were without result. 



Algae. 



Plasmolysis of Algae.* — Dr. J. M. Janse records the interesting fact 

 tliat the protoplasm of the living vegetable cell is permeable to dilute 

 solutions of mineral salts (potassium nitrate and sodium chloride) and 

 of cane-sugar. The experiments were made both on a salt-water alga, 

 Chsetomorpha serea, with which also Lomentaria, TJlva, and Dietyota agree 

 in this respect, and on a fresh-water alga, Spirogyra nitida. In all these 

 instances the plasmolysis, which had at first set up with the solutions 

 named, completely disappeared after two hours. After four days the 

 filaments had regained their previous turgidity ; the terminal cells being 

 swollen to double their original size by the bulging of the transverse 

 cell-walls, without any cell-division taking place. 



Choristocarpus tenellus.f — Herr F. Hauck describes this very rare 

 alga, gathered on Dasya elegans, on the island of St. Catherine, off the 

 coast of Istria. The so-called sporangia with transverse septation he 

 has determined to be gemmae corresponding to those of Sphacelaria. One 

 kind only of zoosporangium was found, the multilocular, on separate 

 individuals. 



New Fresh-water Floridea.t — Herr M. Mobius describes a hitherto 

 undescribed fresh-water alga found growing on the leaves of Aneura 

 pinnatifida. It consists of dichotomously branched filaments of a red, 

 violet, or greenish colour, springing from cushion-like masses. Although 

 presenting analogies to Chantransia, its systematic position cannot at 

 present be ascertained. Cystocarp-like structures were observed, but 

 their exact nature could not be determined. 



Lemanea.§ — Herr F. Ketel corrects one or two points in Sirodot's 

 description of the anatomical structure of this genus of algaa. The 

 thallus grows by means of an apical cell, from which segments are cut 

 off by walls placed at right angles to its direction of growth. Within 

 each segment two walls, curved in the form of a watchglass, which lie 

 in the direction of the growth in length, first of all separate two opposite 

 lenticular cells. By two further transverse septa a " central cell " is 

 formed, surrounded by peripheral cells. The central cell becomes a 

 member of the central axis, the four peripheral cells develope into the 

 "supporting cells" ("ramification cruciforme") ; the hollow cylinder 

 resulting from their further divisions. The thallus may therefore be 

 regarded as composed of a central axis with whorls of four branches 

 which coalesce into the cylinder ; while in Batrachospermum we have 

 free verticillate branching, and only the accessory lateral branches form 

 a cortical layer applied to the central axis. The ooblastema-filaments 

 proceed directly from the impregnated oosphere ; Sirodot does not clearlv 



* Bot. Centralbl., xxxii. (1887) pp. 21-6. 



t Hedwigia, xxvi. (1887) pp. 122-4 (1 pi.). 



\ Versamml. Deutsch. Naturf. u. Aerzte, Wiesbaden, Sept. 21, 18S7. Ber 

 Deutsch. Bot. Gesell., v. (1887) pp. lvi.-lxiv. (1 pi.). 



§ Ketel, F.. ' Anatom. Unters. iib. d. Gattung Lemanea,' Greifswald, 1887. See 

 Bot. Ztg,xlv. (1887) p. 779. 



