82 SUMMARY OF CURRENT RESEARCHES RELATING TO 



autoplast of the chloropliyll-graiiis consists of a light-coloured matrix 

 in whicli are imbedded green grains. The phenomena of swelling and 

 other reactions are explained by the following hypothesis : — Every 

 grain contains an invisible inclosed substance soluble in water ; the 

 solution of this stretches the framework, which swells at the same 

 time, and which forms a relatively dense envelope around the inclosed 

 substance. The oily substances inclosed, he determined not to 

 consist of a fixed (fatty) oil. 



In the passage of autoplasts into anaplasts and chromoplasts, 

 chemical and morphological differences are observable. The former are 

 shown by the different behaviour towards reagents ; the latter consist 

 of a change in the structure, size, and mass of the trophoplast. 



The form of the trophoplast is altered first of all by foreign bodies 

 which grow in or on it. The autoplasts of many plants also undergo 

 a change of form under the influence of rays of light. The position 

 of the trophoplasts within the cells is also not fixed, light and 

 gravitation causing variations in this respect. 



From the investigation of starch-grains in parenchyma-cells of 

 colourless stems, petals, fruits, seeds, and scales, the author draws 

 the conclusion that wherever starch-grains occur, trophoplasts are 

 also present, in or on which the starch-grains grow. The viridescence 

 of ordinarily colourless parts of plants always depends on the trans- 

 formation into autoplasts of anaplasts already present in the colour- 

 less cells. Wherever looked for, in parenchyma-cells, epidermal cells, 

 sclerenchymatous cells, and sieve-tubes, the author always found 

 trophoplasts. 



In all cases where chlorophyll-grains are formed by the investment 

 of starch-grains with viridescent protoplasm, the first stage is always 

 the formation of trophoplasts. Observations on the development of 

 the autoplasts of Allium Gepa and Elodea led to the conclusion that 

 trophoplasts never arise from a differentiation of the protoplasm ; but 

 that they always multiply by division, and, with the protoplasm in 

 which they are imbedded, always pass in a young and small condition 

 into the daughter-cells on the division of a meristem-cell ; there they 

 increase further by division, grow with the cell either into anaplasts 

 or into autoplasts and chromoplasts, and usually disappear with the 

 death of the cell. 



Mechanism of the Splitting of Legumes.* — According to C. 

 Steinbrinck, the splitting of legumes is chiefly the result of hygro- 

 scopic tensions between the ligneous layer and the outer epidermis, 

 alone or together with the hypoderm. These tensions are caused not 

 only by the greater capacity of the ligneous layer for swelling, but 

 depend essentially on the cross position of the cells of both tissues, 

 which contract more in the transverse than in the longitudinal 

 direction. This difference of contraction being greatest in the direc- 

 tion of the tangential transverse diameter of the ligneous fibres, these 

 bring about a spiral curving inwards of both valves of the legume, 

 which causes them eventually to spring asunder. In the different 



* Ber. Deutsch. Bot. Gesell , i. (1883) pp. 270-5. 



