784 SUMMARY OF CURRENT RESEARCHES RELATING TO 



7- General. 



Autumnal Changes in Maple Leaves.* — Messrs. W. K. Martin and 

 S. B. Thomas give the resiilts of certain investigations conducted in the 

 botanical laboratory of Wabash College. The structure of the normal 

 green maple leaf consists of the ordinary epidermal layer above and below, 

 a single cell in depth, a single layer of rather elongated palissade-cells, and 

 usually about three layers of spongy parenchyma, more closely packed 

 than usual. The chlorophyll bodies are small, and thickly and evenly 

 distributed throughout the mesophyll cells. 



The first indication of the approach of autumnal changes is the with- 

 drawal of the contents of the mesophyll-cells. The protoplasm seems to 

 dispose of much of its substance in the manufacture of cellulose, and the 

 chlorophyll-bodies are seen b(jth to disintegrate and to blend together in 

 large masses. In leaves which have become brown, a greater amount of 

 cell-contents remains than in the red, the chlorophyll-bodies do not mass 

 together so much, and the cell-sap is a dirty brown. In red leaves the 

 cell-contents are even more reduced, some cells being almost empty, the 

 remaining contents are mostly collected in masses of considerable size, and 

 are often surrounded by a pellicle of cellulose. The cell-sap is coloured 

 by the characteristic red colouring matter, erythrophyll. In yellow leaves 

 the cell-contents are much like those of the red, but the cell-sap is colour- 

 less, and the chlorophyll-masses are stained yellow by xanthophyll. 



Physiolog'ical Eole of Vine Leaves.j — Herr H. Miiller states that a 

 large number of leaf-bearing shoots should be sacrificed during the ripening 

 of the fruit. These leaves require a large quantity of sugar for their 

 development and for the support of their respiration. In removing the 

 old leaves during the ripening of the fruit, too great a loss of assimilating 

 tissues need not be feared, becaue the old leaves have only feeble assimi- 

 lating power, and are moreover in the shadow of the upper leaves. If two 

 shoots are cut off and placed in darkness until all the starch has disappeared, 

 then one of these simply placed in water, and the other injected with water 

 under pressure, the latter will form starch much more abundantly than the 

 former. The transformation of starch into sugar is similarly affected. 



Influence of soil on the vegetation on the summits of the Alps.l — 

 M. J. Vallot states that the most interesting localities to study the influence 

 of soil on the vegetation of the Alps are those where, in the midst of a 

 uniform region, one finds a patch of soil of a different character. The 

 Aiguilles Eouges which arise over Chamounix, opposite Mont Blanc, are 

 formed of crystalline schist. On the other side, separated by a deep valley, 

 rises the Buet, where the crystalline schist is covered by triassic and Jurassic 

 strata. At the Belvedere, the highest point of the Aiguilles Eouges, a small 

 portion of sedimentary earth remains, and it is interesting to contrast the 

 vegetation of the summit with that of the surrounding district. 



The author then gives three lists of plants. One for the mica schist 

 on the summit of the Belvedere, another for the calcareous schist of the 

 Belvedere, and a third for the Buet. 



The following plants are found only on the mica schist : — Draba fladni- 

 zensis, Semper viv am montanum, Oxyria digyna, Gar ex curvida, &c. ; while 

 Itanunculus glacialis, Arabis alpina, Alsine verna, Campanula cenisia, Linaria 

 alpina, &c., are found on the calcareous, but not on the mica schist of the 

 Belvedere. 



* Bot. Gazette, xii. (1887) pp. 78-81. 



t Ann. Agronom., xiii. p. 140. Cf. Journ. Chem. Soc. Lond., 1887, Abstr., p. 685. 



X Bull. Soc. Bot. France, xxxiv. (1887) pp, 25-9. 



