INVERTEBKATA, CRYPTOGAMIA, MICROSCOPY, ETC. 117 



of the plant that contains it, while its spectroscopic properties are 

 unchanged, Hoppe-Seyler came to the conclusion that on the death of 

 the plant the chlorophyll undergoes a chemical change which is not 

 accompanied by any change in its relation towards light. 



After first removing the wax from grass leaves by ether, and then 

 soaking in hot alcohol, a solution is obtained of two distinct colouring 

 matters. The first, soluble with difficulty in alcohol and ether, and 

 easily precipitated as greenish, silver- white, four-sided crystalline 

 plates, is evidently identical with Bougard's crystals of erythrophyll. 

 Ilie second substance is more soluble in alcohol and ether, from 

 which it crystallizes out in microscopical needles and plates of a dark 

 green colour, brown in transmitted light, and of the consistency of soft 

 wax. They are soluble with difficulty in cold alcohol, more easily 

 when hot, very easily in ether or chloroform. To this substance 

 Hoppe-Seyler gives the name chlorophjJlan ; and to it is due the well- 

 known fluorescence of chlorophyll in light of a refrangibility between 

 the lines B and in the red. It is this constituent of chlorophyll 

 which he believes to possess the power of decomposing the carbonic 

 acid of the atmosphere. 



Function of Chlorophyll, and Action of Light upon it.* — 

 Dr. Pringsheim has recently directed a fresh series of experiments to 

 the elucidation of the function of chlorophyll in the life of the plant, 

 and the connection of its production and destruction with the intensity 

 of light. His method of examination was to expose the structui'e under 

 observation to the jjlane of a solar image projected in the focus of an 

 achromatic lens of GO mm, diameter. 



When, by means of such a lens and a heliostat, an object contain- 

 ing chlorophyll, such as a moss-leaf, fern-prothallium, chara, con- 

 ferva, or section of a leaf of a flowering plant, is exposed to con- 

 centrated sunlight, rapid and energetic changes are seen to take 

 place in it, in a period varying from three to six minutes or more. The 

 first striking eficct is the complete decomposition of the chlorophyll, 

 the result in a few minutes being the same as if the object had lain for 

 twenty-four hours in strong alcohol. The green colouring matter of 

 the grains has entirely disappeared, while the ground-substance of the 

 chlorophyll has undergone but little change. The destructive change 

 then advances to the other cell-contents, ending, if the action of the 

 intense light is continued sufliciently long, in the complete destruction 

 of the cell itself. The circulation of the protoplasm is arrested ; the 

 protoplasm-threads are ruptured; the nucleus is displaced; the 

 I)riuiQpdial utricle (ectoplasm) contracts and loses its impermeability 

 to colouring rnattcis ; the turgidity of the cell ceases ; in short, the 

 cell exhibits all the ^jhcnomeua of rapid and irreparable destruction. 



Pringsheim next proceeds to show that these phenomena are not 

 the direct effects of a high temperature produced in the cell by radia- 

 tion. A similar effect is produced whether the rays have jireviously 

 passed through a red solution of iodine in carbon bisulphide, a green 

 solution of cupric chloride, or a blue animoniacal solution of cupric 

 sulphate, provided only that the light transmitted is of sulficicut 

 ' * ' MH. Akad. Wiss. Berlin,' July 1879, p. 532 ; see ' Ann. auil Mag. Nat. Hist.,' 

 V. (187y)i). <"-• 



