302 SUMMARY OF CURRENT RESEARCHES RELATING TO 



pressure promotes assimilation. The isolated action of the pressure of 

 C0 2 , and the isolated action of the total pressure, are hoth modified in a 

 different way by the amount of C0 2 contained in the atmosphere. But 

 these modifications are of such a nature that the resultant phenomenon 

 follows the same law within broad limits. When air containing C0 2 is 

 simply rarefied, the assimilation passes first through a minimum and 

 then through a maximum. 



Grafting of the Vine.* — According to A. Tompa, when Vitis vinifera 

 is grafted on V. riparia, not only the cambium, but also the xylem, 

 phloem, and pith unite by new formation of healing tissue, or less often 

 locally by direct fusion without any new formation. The healing 

 tissue or callus springs only to a small extent from the cambium ; an 

 essential part in the formation of the healing tissue is taken by the 

 phloem-parenchyme (the medullary rays take part to a less extent) ; 

 while the primary cortical parenchyme and the pith do not again form 

 meristem, or only partially. The fusion culminates in the formation of 

 tracheae and sieve-tubes. The bast-fibre-bundles of the primary cortex 

 and the epiderm are incapable of uniting. 



Ripening of Shoots of the Vine.f — M. L. Kovessi points out that a 

 good crop of grapes, as of any other fruit, depends on favourable mete- 

 orological conditions, as to temperature and heat, of two successive 

 summers. In order to produce and ripen an abundant crop of fruit, 

 the branch must have been subjected to good conditions for ripening 

 (aoutement) during the previous summer. This ripening consists of a 

 due thickening of the cell-walls and an abundant supply of starch in the 

 cells. An ill-ripened branch is one whose growth has been arrested at 

 an early stage in the differentiation of its tissues. As a rule (in the 

 vine) the first and last buds on a branch (i.e. those nearest to the base 

 and to the apex) are not fertile ; it is only the intermediate ones that 

 develope into fertile branches during the following summer. 



Vitality of Seeds.J — Dr. A. D. Waller has carried out an extensive 

 series of experiments for the purpose of determining whether " blaze- 

 currents " may be used as a sign and measure of the vitality of seeds. 

 By a " blaze-current," Dr. Waller denotes " the galvanometrical token 

 of an explosive change locally excited in living matter." He found the 

 physiological effect of the blaze-reaction on germinating beans proved 

 by (1) the influence of raised temperature ; (2) its general parallelism 

 with germination tests ; (3) the influence of lowered temperature ; (4) 

 the influence of anaesthetics ; (5) the influence of strong electrical 

 currents ; (6) the absence of blaze and the failure of germination in 

 water-logged seeds. There was found to be a general, but not absolute, 

 correspondence as regards magnitude, between the blaze-reaction and 

 the genninative activity. 



Sensitiveness of Plants to Mineral Substances. — In opposition to 

 the statement of M. Boehm, P. P. Deherain and M. Demoussy § find 



* Ann. Inst, centr. Ampslologique, i. (1900) Budapest,* No. 1 (6 pis. and 

 numerous figs.). See Bot. Ztg., lix. (1901) 2" Abt., p. 26. 

 t Comptes Rendus, cxxxii. (1901) pp. 647-50, 923-6. 

 X Proc. Roy. Soc, lxviii. (1901) pp. 79-92 (3 figs.). 

 § Comptes Rendus. cxxxii. (1901) pp. 523-7. 



