BOTANY. 477 



applied the term episfrophc to the distiibiUiou of the grains ui)oii tlie 

 free walls of the cells, and aposfrophe to the arrangement on the side 

 walls. Apostrophe i)rodaced by strong illnminatiou Moore proposed 

 to call positive and that produced by weak illumination, ne<jatice. He 

 coins the word plujtolysiH for the whole of these ])henomena. Tie also re- 

 investigated the question as to whether the grains are drawn along pas- 

 sively with the streaming plasma, or whether they possess the power 

 of independent motion. He finally adopts the conclusions of Sachs, 

 Pfeffer, and others, that they are drawn along passively. 



The nucleus has been the subject of numerous experiments and stud- 

 ies. Thus Zacharias (Bot. Zeit. xly.) has investigated its structure 

 and concludes that the cell-nucleus of both plants and animals is com- 

 posed of two distinct substances, which he calls plastin and nuclin, which 

 remain undissolved after treatment with artificial gastric juice. The 

 nuclin forms the colorable filament loups of the nucleus that remain 

 after treatment with artificial gastric juice or hydrochloric acid, sharply 

 defined and shining in appearance. It also readily absorbs certain pig- 

 ments, especially methyl-green. Plastin,on the other hand, is an essential 

 constituent of the entire protoplasmic cell-contents, and differs from 

 nuclin in its action under reagents. The prevalent theory that the vital 

 l)roperties of the cell are derived from the nucleus has been confirmed 

 by Klebs (Biol. Ceutralbl.), who plasmolysed living cells of Zygnemia 

 with a solution of sugar. The effect of the plasmolysis was to cause 

 the cell-contents to contract and separate into t^o halves, each contain- 

 ing one of the two chlorophyll bodies, while the whole of the nucleus 

 was contained in one of the halves. The half cell containing the nucleus 

 soon regained its activity and surrounded itself with a new cell-wall. 

 The half-cells destitute of nucleus, while they retained their vitality 

 for a considerable time and even ])roducedan abundance of starch, never 

 started to grow, and could not secrete a new cell-wall. Zacharias has 

 still more recently studied the part taken by the nucleus in cell-division 

 (Ber. deutsch. Bot. Gesell. v.). He confirms the earlier observations 

 that the cell protoplasm does not penetrate into the nucleus during its 

 division. Haberland (op. cif.), has studied the position of the nucleus 

 in mature cells and reaches the conclusion that their })osition is not ar- 

 bitrary, but depends on its function as the bearer of the idioplasm which 

 governs development. The young condition of the vacuoles has been 

 investigated by Went (Arch. Neerland, xxi.). He finds, contrary to 

 the general opinion, that minute vacuoles are present in the youngest 

 cells, for exami)le, in the growing i)oint. He also found vacuoles in 

 oospheres, pollen-grains, and catnbium-cells. Halsted has recorded 

 (Bot. (iaz. XII.) the finding of three nuclei in pollen-grains of Sambiwufi 

 raeemosa. 



Chlorophyll has also been made the subject of recent investigation. 

 Tschirch has given (Ber. deutsch. Bot. Gesell., Y) a resume of recent 

 studies on the composition of chlor()i)hyll, and concludes that iron is 



