570 SUMMARY OF CURRENT RESEARCHES RELATING TO 



Protophyta. 

 a. Schizophyceae. 



Boundary-cells and Cell-contents of the Cyanophyceae.* — F. Brand 

 has investigated the appearance and structure of the " boundary-cells " 

 (Grenz-zellen) found in almost all species of Nostocacete. He observed in 

 Nostoc commune tsvo different kinds of vegetative cell, one considerably 

 smaller than the other, and producing filaments of smaller diameter. 

 These latter arise from the division of the contents of heterocysts 

 which occur in the outer layers of the colony ; their cells gradually in- 

 crease in size until the filaments attain the ordinary diameter. Some 

 of the heterocysts do not break up, but remain in connection with the 

 neighbouring vegetative cells by threads of protoplasm passing through 

 the cell-wall ; these vegetative cells then become capable of multiplica- 

 tion under favourable conditions. Similar phenomena occur in some of 

 the Scytonemese. 



With regard to the occurrence of red granules in the " water-bloom," 

 resulting from the accumulation of some species of Cyanophyceae, the 

 author dissents altogether from the theory that they contain some 

 special gas. In Polycyslis ochracea and Anabsena flos aquse they make 

 their appearance at first only in the periphery of the colony ; in the cen- 

 tral cells only when the colony is fully developed. Similar red granules 

 occur in Pltormidium ambiguum, Lyngbya sestuarii, and Oscillatoria prin- 

 ceps, which do not form " water-bloom " ; also in the " boundary-cells " 

 of Nostoc commune. The nature of the pigment was not determined. 



/3. Schizomycetes. 



Light of the Phosphorescent Bacteria of the Baltic.j — G. Tarchanoff 

 gives an abstract of a series of observations on the influence of dif- 

 ferent conditions on the luminous activity of bacteria from the Baltic. 

 Fresh cultures give the strongest light, especially when the bouillon is- 

 kept moving and is mixed with air. The light may last from two weeks 

 to three months. It is a manifestation of respiration, and is closely 

 associated with the consumption of oxygen ; its appearance is apparently 

 periodical, but without any regularity. When at rest the luminous 

 layer is limited to the surface of the bouillon. These bacilli are more 

 resistant to cold than to heat, their optimum temperature being 7°-8° C. 

 Daylight appears to be harmful. Some chemical agents, such as chloro- 

 form, ether, alcohol, potassium cyanide, rapidly extinguish the light, as 

 also do bile, carbonic acid, and acids generally. To many other 

 chemical reagents the light is indifferent. Strong induced and gal- 

 vanic currents drive it to the negative pole, from which it after a time 

 disappears. The extinction of the light, is, however, not due to loss of 

 vitality, for the introduction of air causes the reappearance of the light. 

 Mechanical movement is followed at first by increase of light, but after 

 a time by dimness and extinction. 



Frogs may be rendered luminous by introducing into the dorsal 

 lymphatic sacs a few cubic centimetres of luminous bouillon. The whole 



* Ber. Deutsch. Bot. Ges., xix. (1901) pp. 152-9 (4 figs.), 

 t Comptes Rentlus, cxxxiii. (1901) pp. 296-9. 



