102 SUMMABT OF CURRENT RESEARCHES RELATING TO 



not identical witli sinistrin and lactosin. Of all the carbohydrates 

 starch must have the largest molecular weight, probably GCgHioOg + 

 H2O; but it may be considerably higher even than this. It was 

 further determined that the diffusibility of the various carbohydrates 

 is in inverse proportion to their molecular weight. In the spring- 

 sap of many trees, cane-sugar is present to the extent of 2 "5 per 

 cent. ; while the carbohydrates chiefly employed for the storage of 

 food-material are those with a high molecular weight — starch, inulin, 

 lactosin, and sinistrin. 



Function of Tannin.* — Herr G. Kraus argues that tannin is not, 

 as is generally thought, simply a waste product of excretion in the 

 plant, but that it plays an important part in the formation of food- 

 material, that it is, in fact, of the nature of a reserve-substance. This 

 is shown by the parts of the plant in which it is very frequently 

 found, as for example, in the growing point of the stem, in the inter- 

 fascicular cambium, and especially in the phellogen. In leaves it 

 occurs especially in the palisade-tissue; it is also found in those 

 tissues which serve for the conduction of formative substances, as in 

 the soft-bast and in the starch-sheath. Not unfrequently also it is met 

 with in true receptacles for reserve-material. Its distribution can 

 best be compared with that of starch or sugar. It can be transformed 

 in quantities from place to place ; and its production is closely con- 

 nected with light. Its quantity diminishes rapidly in leaves or shoots 

 placed for any time in the dark. In etiolated plants it is altogether 

 wanting. It is formed in the organs exposed to strong light, as 

 the leaves, and from there readily transferred to other parts of the 

 plant. 



Physiological Functions of the Starch-sheath.f — Herr H. Heine 

 calls attention to the fact, already described by Sachs and others, of 

 the invariable occurrence of a single row of cells — denominated by 

 Sachs the starch-sheath — in immediate apposition to the vascular 

 bundles, and, with their sieve-tube portion, accompanying these tubes 

 throughout their whole length. These cells are always strongly 

 charged with starch-grains, or occasionally with glucose. A careful 

 examination of the facts connected wdth the appearance and dis- 

 appearance of the starch from this layer of cells has led the author 

 to the conclusion that the starch contained in the starch-sheath must 

 be regarded as a store of reserve-substance, furnishing the material 

 for the thickening, which is often very considerable and rapid, of the 

 young bast-cells in their immediate proximity. This conclusion is 

 favoured by the anatomical structure of the starch-cells, and especially 

 by the close way in which they fit to one another, and to the adjoining 

 phloem-cells, without any intercellular spaces. 



Gro'vs/'th of Leaves.! — According to Herr J. Kraus, the leaves of 

 the Scotch fir are larger in their second and third than in their first 



* Ber. Sitz. Natiirf. Gesell. Halle, 1884, pp. 46-57. 

 t Ber. Deiitsch. Bot. Gesell., iii. (1885) pp. 189-94. 



X Abhandl. Naturf. Gesell. Halle, xvi. (1884) pp. 46-57. See Bot. Centralbl., 

 xxiii. (1885) p. 132. 



