642 SUMMARY OF CURRENT RESEARCHES RELATING TO 



not assimilate it is probably tbo nucleus that supplies the matorial 

 which is subsequently transformed into starch, either from the 

 chromatophorcs or from the cytoplasm. The chlorophyll-grains may 

 either lie on tho cell-walls bounding intercellular spaces — epistrophei 

 or on those bounding other cells — apostrophe. Light may cause 

 movement of the chlorophyll-grains in two ways : — either dependent 

 on the structure of the organism, and without reference to the 

 direction of impact of the light —phototonic, or resulting entirely 

 from the direction of the rays of light — phototactic. The apostro- 

 phic or epistrophic arrangement is the result of complicated laws 

 dependent on the action of light ; very strong irritation of light 

 causes the chlorophyll-grains to collect into one or two lumps, a 

 phenomenon for which Schimper proposes the term systrophe. 



The result of a number of observations on this subject leads the 

 author to the conclusion that light causes two quite distinct kinds of 

 movement in the chlorophyll-grains ; on the one hand the grains 

 tend to move towards certain definite parts of the cell, varying 

 according to the intensity of the light : — phototonic movements ; on 

 the other hand to place their broad surfaces parallel or vertical to the 

 direction of the rays of light : — phototactic movements. The photo- 

 tonic movements are identical with those caused by a decrease in the 

 intensity of the light, by cold, and other sources of irritation ; this 

 identity depending on a specific energy of irritation. Movements of 

 the phototactic description are, on the other hand, not produced by 

 any other factor except light. 



Formation of Starch-grains in leaves from Sugar, Mannite, and 

 Glycerin.* — Herr A. Meyer shows that the leaves are able to form 

 and to store up starch, not only from glucoses and cane-sugar, but 

 also from mannite and glycerin. He concludes that the starch formed 

 in leaves is the last member of a long series of compounds which are 

 successively produced in the assimilating cells out of the carbon of 

 the carbon dioxide of the air and other elements. The intermediate 

 stages are very different in different plants. 



By applying Sachs's test for starch to Bohrn's method of using 

 sugar-solutions, the author shows that there are leaves which produce 

 starch out of dextrose as well as out of levulose and galactose, if laid 

 for a considerable period in the dark on solutions of these carbo- 

 hydrates. Other leaves, again, will obtain starch out of only one or 

 two of these carbohydrates ; and the plants in the cells of which any 

 one of these kinds of sugar is found are especially capable of obtaining 

 starch out of this particular kind. No plant was found able to form 

 starch out of inosite. From cane-sugar all the leaves examined were 

 able to form starch, also from maltose ; but none from milk-sugar or 

 melitose. 



From mannite the leaves of all species of Oleacea^ examined which 

 contain this substance were able to produce starch, while negative 

 residts w r ere obtained with the leaves of other plants which do not 



* Bot. Ztg., xliv. (1886) pp. 81-88, 105-13, 129-37, 145-51. Cf. tin's Journal, 

 ante, p. 101. 



