1883.] 



Note on the Constitution of Chlorophyll. 



183 



that a continuity of the protoplasm between adjacent cells occurs in 

 Dioncea muscijpula, being especially pronounced in the most central 

 layers of parenchymatous cells. 



The parenchyma cells of the petioles of certain plants which, as 

 H. von Mohl showed, are often thick walled and conspicuously 

 pitted, afforded favourable material for investigation. In Aucuba 

 japonica, and Prunus lauro-cerasus, distinct threads could be made out 

 crossing the pit- closing membrane. In Ilex aquifolium there was a 

 doubtful striation, and in the rest examined a mere coloration of the 

 pit-membrane. 



Examples of continuity have thus been shown to exist in ordinary 

 parenchymatous tissue ; and this materially strengthens the belief that 

 the phenomenon of the connexion of cells with one another is one of 

 universal occurrence. 



As to the function of the filaments, the author believes that in 

 sieve-tubes and in endosperm-cells they may make possible a trans- 

 ference of solid materials, besides establishing a protoplasmic com- 

 munication ; but in ordinary cells the only significance of the threads 

 is, that by their means the protoplasm of isolated cells becomes con- 

 nected, and that thus the communication of impulses from one part 

 of the plant to another is insured. 



Finally, the presence of these minute perforations of the cell-wall 

 need not lead to any modification of our general ideas as to the 

 mechanics of the cell. 



V. "Note on the Constitution of Chlorophyll." By Edward 

 Schunck, F.R.S. Received December 6, 1883. 



An examination of some products derived from chlorophyll, which 

 has occupied me for some time, has led to the question of the true 

 nature and constitution of chlorophyll, a question on which widely 

 different opinions prevail. Without entering into matters which 

 concern the physiologist only, it may be said that to the chemist 

 chlorophyll is simply an organic colouring- matter, the substance to 

 which the green colour of leaves and other parts of plants is due. 

 Now colouring-matters are of three kinds. To the first class belong 

 such as occur ready formed and in a free state in vegetable and animal 

 organisms, such as the colouring-matters of turmeric and safflower. 

 The second class comprises those that are formed from colourless 

 chromogens by the combined action of alkalis and oxygen, the 

 colouring-matters of log- wood and archil being well-known examples 

 of this class. These colouring-matters change rapidly when exposed 

 to the further action of oxygen in the presence of alkali, but are quite 



vol. xxxvi. 



