ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 817 



the peripheral layer of merismatic cells ; Cambium of parenchymatous 

 cells with narrow cavity, usually united into longitudinal bundles ; 

 Fundamental parenchyma is the tissue which remains after the differ- 

 entiation of the protoderm and cambium. 



Chlorophyll and Hypochlorin.* — A. Tschirch gives the follow- 

 ing as the results of a series of fresh observations on chlorophyll and 

 its derivatives. 



Pringsheim's hypochlorin (at all events as regards the greenish 

 yellow needles) is a product of the action of acids on the colouring 

 matter of chlorophyll, and can be produced outside the plant in the 

 well-known crystals. To distinguish this from the possible colour- 

 less matrix, which has, however, not yet been satisfactorily separated, 

 the author calls it a-hypochlorin. It is identical with Hoppe-Seylers 

 chlorophyllan, and with the precipitate which appears spontaneously 

 when solutions of chlorophyll have stood for some time. All the 

 substances belonging to this group are products of oxidation of a 

 portion of the chlorophyll. Chlorophyllan, or a-hypochlorin, can 

 easily be obtained pure in the form which Pringsheim has described, 

 by laying leaves of grass which have been freed by ether from oil 

 and wax, for some days in hydrochloric acid, carefully washing out 

 the acid, and extracting with boiling alcohol. When the filtrate 

 cools abundance of a-hypochlorin precipitates, which can be increased 

 by distilling off a portion of the alcohol. It crystallizes in the form 

 of dark brown (or greenish in incident light) radiating needles ; the 

 whip-like form results from the impurity of the solution. 



The formation of chlorophyllan in the living plant is due to the 

 presence of organic acids. With the exception of water-plants, the 

 author found none in which the cell-sap has not a distinct acid 

 reaction. When the proportion of acid is only small, the chloro- 

 phyllan is only formed by allowing the extract to stand for a long 

 time ; carbonic dioxide produces it at once. The extracts of strongly 

 acid leaves like those of Aesculus or Bumex, deposit chloryphyllan 

 simply on cooling. The formation is completely prevented by giving 

 an alkaline reaction to the extract. 



It is probable that many of the described modifications of chloro- 

 phyll depend on the variation in the proportion of acid present in 

 the cell-sap, and in the variable solubility of the acids in the solvents 

 employed. 



The cause of the absence of hypochlorin from the chlorophyll- 

 grains in many plants, even when lying in an acid cell-sap, is the 

 fact which Tschirch has established, and which had already been 

 assumed on theoretical grounds by Naegeli and Pfeffer, that every 

 grain of chlorophyll is surrounded by a colourless hyaloplasmic 

 layer, which may frequently be clearly made out, especially in water- 

 plants. In the living state this hyaloplasmic layer is not permeable 

 to acids ; it is consequently only after death that the acid cell-sap 

 enters and produces a-hypochlorin. 



In a subsequent communication Tschirch further criticizes Prings- 



* SB. Bot. Ver. Prov. Brandenburg, 1882, pp. 41-5, 124-34. 



