ZOOLOGY AND BOTANY, MICROSCOPY.. ETC. 229 



Mesogerron, a new Genus of Chlorophycese.* — Among other Algae, 

 iu a ditch near Munich, Herr F. Brand finds a species which, under the 

 name Mesogerron fluitans g. et sp. n., he makes the type of a new genus 

 with the following diagnosis : — Thallus aquaticus, simplex v. parce ra- 

 mosus, e cellnlarum serie simplici eonstitutus ; celluhe chlorophorum 

 singulum, axile, rectangnlariter laminiforme, et vario modo levitcr curva- 

 tum, pyrenoidibus destitututn foventes ; generatio ignota. In its double 

 rhizoids, Mesogerron recalls the Ulotrichaceae, but is distinguished from 

 all the species of that group by its vegetative branching, by the central 

 chlorophore, and by the absence of a pyrenoid. 



Differentiated Proteinaceous Substances in Derbesia.j — Herr F. 

 Noll confirms the statement of Kiister as to the occurrence of well- 

 developed sphaerocrystals in the cell-sap of Derbesia ; and he also finds 

 them only in that genus and in Bryopsis among Siphoneae. They are 

 not, however, the result of the disorganisation of protoplasm, but are 

 already present in the cell-sap. The fibre-like structures which accom- 

 pany the sphaerocrystals arise in the form of small needles, which swell 

 up, become mucilaginous, and lose their definite outline. These struc- 

 tures and the sphaerocrystal differ in their staining reactions. 



Acetabularia.J — From a study of Acetabularia mediterranea from the 

 Lucira Islands, Prof. T. Ito concludes that the prototype of this alga 

 probably consisted of a main axis bearing whorls of foliar appendages, 

 which, after discharging its function as an assimilating oi'gan, became 

 converted into a gametange, which represents the cap. Thus the cap of 

 Acetabularia serves a double physiological function, viz. in storing up 

 food as an assimilating organ, and in producing and discharging gametes 

 as a reproductive organ. 



Microdictyon umbilicatum.§ — Herr G. Bitter supplies a contribu- 

 tion to our knowledge of this representative of a little known genus of 

 siphoneous algae. The growing apices of filaments have a remarkable 

 propensity to pass into a rhizoid-like condition. These growing apices 

 are influenced in the direction of their growth by adjacent portions of 

 the thallus, usually curving towards the nearest thallus-portion; and the 

 same is the case also with protrusions from young tubes. The cause of 

 this bending is probably chemotropic The network of hyphae has a 

 strong tendency to become duplicated. 



Vegetative Multiplication of Pandorina morum. || — Herr B. 

 Schroder has followed out the hitherto but imperfectly known mode of 

 non-sexual propagation in this freshwater alga. In its unicellular con- 

 dition (chlamydomonas stage) it loses first its vacuoles, then its eye- 

 spot, and finally its cilia. It then divides successively into 2, 4, 8, and 

 16 (gonium stage) cells. Four of these cells occupy the centi-e of the 

 colony, surrounded by the remaining twelve. In this condition the cells 

 aoain acquire cilia, eye-spots, and vacuoles in succession, forming a 

 mature colony which again breaks up into its constituent cells, each 



* Hedwigia, xxxviii. (1899) Beibl., pp. 181-4 (1 fig.). 



t Ber. Deutsch. Bot. Gesell., xvii. (1899) pp. 302-ti. Cf. this Journal, 1899, p. 515. 



X Hedwigia, xxxviii. (1899) Beibl., pp. 184-6 (English). 



§ Pringsheim's Jalirb. f. wiss. Bot., xxxiv. (1899) pp. 199-235 (1 pi.). 



|j J.B. Scales. Gesell. Vuterl. Cult., 1898 (.1899), Zool.-bot. Sect., pp. 27-30. 



