ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 467 



where a thick string of protoi)lasm occurs in the centre of the cells, 

 dividing at the end into fine branches. (4) In the hairs of Petunia 

 hybrida and cells of the rhizome of Acloxa, broad currents radiate from 

 the nucleus, composed of a number of fine independent streamlets quite 

 distinct from one another. (5) The revolution of the entire contents 

 of a cell round its centre, as in ^tJialium septicum and Euglena viridis. 

 (6) The movement of protoplasm dependent on light, which causes 

 the change of position of the chlorophyll-grains. (7) The movement 

 of minute strongly refractive granules irregularly and independently 

 in the protoplasm in various directions. 



The author states that these currents commence on the formation 

 of the vacuoles, and that the protoplasm and cell-sap are not separated 

 by a membrane of any kind. He attributes them to a periodical change 

 in the capacity of protoplasm for absorption. 



Origin of Chlorophyll-grains. * — Herr K. Mikosch has in- 

 vestigated the mode of origin of chlorophyll- grains, and has come to 

 a different conclusion from Schimper and Meyer, f that they always 

 arise from the division of grains already in existence. For his 

 preparing fluid he employed a dilute 5-10 per cent, solution of cane- 

 sugar, which causes no contraction during the first twenty minutes, 

 and does not in the least disturb the protoplasmic currents in 

 uninjured cells. A very instructive object for observation is the 

 cotyledons of Helianthus annuus. 



If sections are first freed of oil by ether, and then placed in 

 glacial acetic acid, the aleurone-bodies are dissolved, and there 

 remains an undifferentiated reticulation of protoplasm. At a some- 

 what later stage of development numerous granules are seen in the 

 parietal layer which approach one another in places, and later still 

 the homogeneous network becomes also granular, and in the meshes 

 are seen larger or smaller very ill-defined protoplasmic bodies of 

 various forms, which are the young chlorophyll-grains, and become 

 green in the light. 



In the very young leaves of Allium Cepa there are also no 

 differentiated protoplasmic structures to be seen ; what were described 

 as such by Meyer were drops of oil. The protoplasm of the young 

 meristem-cells at the base of the leaf has a framework structure, 

 and particular parts of the framework develope into chlorophyll- 

 grains. The growing-points of Elodea and the young leaves of Zea 

 were also found free of starch- generators. In the latter the starch 

 which is conveyed from the endosperm to the young leaves can 

 become organized at any sjDot, and especially where the protoplasm is 

 densest, into starch-grains and chlorophyll-grains. Under other 

 circumstances also he found that starch-grains are produced without 

 the previous presence of starch-generators. 



Amount of Chlorophyll in Leaves. $ — Dr. A. Hansen has carried 

 out a series of experiments for the purpose of determining this point, 



* SB. K. Akad. Wiss. Wien, i. (1SS5) 30 pp. (2 pis.). 



t See this Journal, iii. (1883) pp. 238, 525 ; iv. (1884) p. 81. 



X SB. Phys.-mcd. Gesell. Wiirzburg, 1885, pp. HO-4. 



