528 SUMMARY OF CUEEENT EESEAECHES EELATING TO 



carbonate in the wood of dicotyledonous trees is not a rare pheno- 

 menon ; but that it takes place only in the duramen or in parts of 

 the alburnum which resemble the duramen in properties. In knots 

 and wounded parts it is frequently separated in considerable quan- 

 tities. It is deposited especially in the vessels and tracheides, less 

 often in the libriform, parenchyma, and medullary rays. It occurs 

 abundantly in the pith when the wood that is in immediate proximity 

 to it assumes the nature of duramen, and becomes filled with lime. 

 An account is given of the different woods in which calcium carbonate 

 was found. 



Hypochlorin.* — The investigations of Pringsheim f on the nature 

 and mode of formation of hypochlorin have been gone over by A. B. 

 Prank, with the following results : — 



The hypochlorin reaction is found by Frank to bear the most 

 intimate relation to the presence of the colouring matter of chloro- 

 phyll ; and this connection is the only constant one, there being no 

 relation to the presence or absence of conditions of assimilation. 

 Hypochlorin is never present in any other part of the protoplasm 

 than in that which is coloured by the chlorophyll-pigment, and here 

 it appears to be universal, whether the chlorophyll be in the form of 

 grains or spiral bands or in the amorphous condition. The hypo- 

 chlorin reaction manifests itself along with the very first trace of the 

 green colour in the young protoplasm, as was demonstrated in terminal 

 buds of Elodea canadensis, where the cells of the young minute leaves 

 are still in a merismatic condition, long before the differentiation of 

 the chlorophyll into grains, and when it is improbable that any 

 assimilation can take place. Hypochlorin is also found in the cell 

 till the close of the existence of the chlorophyll-pigment, in conditions 

 which exclude the possibility of assimilation. 



The hypochlorin reaction is invariably accompanied by a destruc- 

 tion of the colouring matter of the chlorophyll. The first effects of 

 acids on chlorophyll-grains is a change of the green colour into 

 yellowish green or yellow, and this is followed by the separation of 

 oily drops of hypochlorin. If, however, the cells are killed, no 

 separation of hypochlorin takes place. 



Two conditions are therefore necessary for the separation of 

 hypochlorin : — the living condition of the chlorophyll-grain, and the 

 presence of an acid. The reaction may be induced by hydrochloric, 

 sulphuric, nitric, phosphoric, acetic, lactic, tartaric, citric, picric, or 

 salicylic acid, and with very various degrees of concentration. The 

 cause of the change of colour of leaves in autumn is the disappearance 

 of the protoplasm from the cells,, in consequence of which the chloro- 

 phyll-grains come into contact with the acid cell-sap. The same 

 changes take place when leaves become yellow from want of light. 

 The author believes that in this case the chlorophyll is not destroyed 

 directly by the want of light, but only by the secondary action of the 

 acid cell-sap in consequence of the destruction of the protoplasm. 



* SB. Bot. Ver. Prov. Brandenburg, xxiii. (1822) pp. 11-16. 

 f See this Journal, iii. (1880) pp. 117, 480; i. (1881) p. 479. 



