476 RECORD OF SCIENCE FOR 1887 AND 1888. 



united to the cell-protoplasm ; (3) this intraiiinral protoplasm appears 

 in some cases capable of growth on its own account; (4) possibly the 

 cell-wall is formed in the same way as the starch grain. Pechi (Atti 

 Soc. Tosc. Sci. iSTat., viii) has very recently studied the thickening of 

 cell-walls in the leaf-stalk of Aralia. During the early stage of growth 

 the thickening takes place mainly in the angles, but later distinct lay- 

 ers of cellulose are formed within each cell, which soon becomes ligni- 

 fied. From this the author concludes that in the earlier stages the 

 thickening is mainly by intussusception, and during the later stages 

 probably by opposition. On the other hand, Noll (Abhandl. Sencken. 

 burg Xaturf. Gesell. xv) concludes, from an experimental application 

 of staining reagents, that growth takes place chiefly by o})position, and 

 the part played by intussusception is unproved. Krabbe has also 

 studied the structure and growth of the cell -wall (Pringsheim's Jahrb. 

 f. Wiss. Bot., XVIII). He investigated especially the process of increase 

 in thickness in the walls of the bast cells of the Apocynacew and As- 

 clepiadacc(r, and found them to be composed of lamella^ which are 

 themselves made up of lamelhe. These lamellfe apparently arise by 

 fresh formations from the protoplasm. Intussusception he regards as 

 playing only a subordinate part, and must be confined to the innermost 

 lamella^. Zimmermann has an exhaustive treatise, "Die Morphol. u. 

 Physiol, d Pflanzenzelle," which forms the third volume of Schenck's 

 " Handbuch der Botauik." It treats very fully of the structure and 

 chemical composition, as well as the physiology of the cell. 



The morphological and chemical comi)osition of protoplasm has been 

 treated of at great length by Schwarz (Beitr. z. Biol. d. Pflanzen, B. 

 V). He has given many details of the action of various reagents upon 

 protoplasm .and its various modifications, only a few of which may be 

 here enumerated. The varying acid or alkaline reaction of cell-sap he 

 attributes to the substances in solution in it, such as pigments. The 

 protoplasm he has found to be always alkaline in reaction, as also is the 

 cytoplasm, nucleus, chromatophores, and in some cases the protein- 

 grains. The chlorophy] the author regards as having a fibrillar struct- 

 ure composed of what he calls chloroplastin. The nucleus is composed 

 of several substances, among which he recognizes chromatin, pyreuiu, 

 linin, and paralinin. The cytoplasm is made up of three substances: (1) 

 the cell-sap, (2) the microsomes, insoluble in water and the cytoplasm ; 

 (3) the cytoplastids. All the nuclear substances, with the exception 

 of chromoplastin and cyto])lastin, are soluble in concentrated potash- 

 lye, or a 10 per cent, solution of sodium chloride. 



"The influence of light upon protoplasmic movement," in Journ. Linn. 

 Soc. Loud., XXIV, is the title of a long paper by Moore. The well- 

 known circumstance of the chlorophyll grains becoming collected into 

 masses in sunlight and being more or less dispersed in darkness has 

 been very fully re-investigated, and the conclusion reached is that these 

 displacements are more the result of illumination than heat. Frank 



