54 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
till after germination. It then occurs in tlie primary meristem and 
cambium, especially at the apices of tbe roots, and at tbe spots where 
the secoiidaiy roots are being formed ; in the older parts it often dis- 
appears entirely. The primary tannin (in Kraus’s sense) may be formed 
in the same cells and groups of cells as the secondary, as, for example, 
in the vascular-bimdle-sheath and the epiderm. The young cork-cells 
often contain a rather large quantity of tannin, which disappears later, 
and without being transferred elsewhere. When vessels are formed, 
the tannin disappears with the living protoplasm. In the pith, the 
cortical parenchyine, and the collenchyme, the tannin often decreases 
in quantity, but without the protoplasm also disappearing. There 
appears to be some analogy between tannin-sacs and bundles of raphides, 
but none between the former and starch. 
Colouring-matter of the Cones of the Scotch Fir.^' — Sig. L. Macchiati 
finds the colouring-matter of the cones of Abies excelsa to consist of a 
mixture of at least three pigments — a beautiful orange-red substance, 
insoluble in alcohol, ether, or chloroform, but very soluble in water, 
out of which it crystallizes ; an unerystallizable substance of a resinous 
nature ; and a golden-yellow unerystallizable substance soluble in 
water, but insoluble in alcohol, ether, and chloroform. In addition to 
these there is a substance of a waxy nature. 
Function of Calcium Oxalate in Leaves.| — According to Sig. A. 
Alberti, secondary calcium oxalate is formed only in the assimilating 
cells, under the action of light; its accumulation is not promoted by 
transpiration. The crystals of calcium oxalate can be relissolved, 
when they fulfil a physiological function through their lime, not through 
their acid. This consists in aiding the transport of the carbohydrates 
from the assimilating tissue towards the reservoirs of food-material, and 
that of the nitrates, phosphates, and sulphates to the assimilating tissue. 
The lime, abandoned by the respective acids, which have furnished the 
elements for the formation of the more important plastic substances, 
combines with oxalic acid, which is a product of regressive metamor- 
phosis. 
(3) Structure of Tissues. 
Mechanical Tissue-system.^ — Herr H. Mertins has investigated the 
function of the pores commonly found in the walls of bast-cells which 
are supposed to have a mechanical function only, and where, therefore, 
they could not serve primarily for the transport of food-materials. He 
finds that, as regards the apparent relationship of the mechanical tissue 
to the transport of sap, two types may be distinguished: — (1) A distinct 
stereome-cylinder which completely separates the conducting from the 
assimilating tissue ; and (2) a stereome-cylinder with ribs projecting to 
the epiderm, outside of which is the assimilating tissue. The first type 
occurs only in certain CaryophyllaceiB ; and it is in them only that the 
mechanical cells have a direct function in connection with the transport 
of food-material. As compared with the second type, the pores in the 
* Nuov. Giorn. Bot. Ital., xxi. (1889) pp. 423-7. 
t Boll. Soc. Ital. Mierosc., i. (1889) pp. 30-44. Cf. this Journal, 1889, p. 774. 
X ‘Beitr. z. Kenntniss d, mechanischen Gewebe-systems,’ Berlin, 1889, 42 pp. 
See Bot. Centralbl., xl. (1889) p. 145. 
