344 SUMMARY OF CURRENT RESEARCHES RELATING TO 



in the cells of the host-plant. The stain, which is very dark and always 

 fugitive, is due to an organic substance excreted by the cell and impreg- 

 nating the cell-walls. The observations were made on Sphacelaria 

 Hystrix parasitic on Cystoseira ericoides, on S. furcigera parasitic on 

 C. discors, and on S. ampliicarpa sp. n. parasitic on Halidrys siliquosa. 

 The conclusion arrived at was that the parasitic alga induces, in some of 

 the cells of the host-plant with which it comes into contact, the produc- 

 tion of the same peculiar substance as a product of excretion. No similar 

 reaction was exhibited by other algae epiphytic on the Sphacelaria. 



Elasticity of Tension of Vegetable Organs.* — Dr. L. Nicotra gives 

 formulas for the elasticity of vegetable tissues. As a general conclusion 

 he states that the amount of distension would be injurious to a plant if 

 it were not counteracted by a proportionate elasticity. The elastic 

 resistance of the distended cell-wall is one of the most important factors 

 in turgor. Continuous distension without elasticity would be injurious 

 to the plant. To obviate such injury, the pressure is regulated by the 

 law of periodicity, rendering it possible to return to the physical con- 

 ditions which are favourable to further growth. 



Modification of Tissues by a Longitudinal Strain.t — M. Thouvenin 

 describes the changes induced in the structure of a stem of Zinnia elegans 

 by subjecting it to a moderate traction in the direction of its axis. As 

 a general result it may be stated that it causes a diminution of the peri- 

 cyclic stereome and retards the development of the secondary fibro vascular 

 bundles. The diameter of the vessels is somewhat increased ; while the 

 medullary rays are rather broader, not having been used up in the forma- 

 tion of the secondary vascular bundles. 



C4) Structure of Organs. 



Female Flower of Salisburia.:}: — Prof. R. v. Wettstein describes a 

 number of abnormalities in the female flower of Salisburia adiantifolia 

 (Ginglco biloba), from which he draws the following conclusion. The 

 normal flower consists of a structure homologous to a shoot which bears 

 merely two transverse carpels. Each carpel bears normally a single 

 ovule. The separation of the two carpels, and the stalk-like develop- 

 ment of their bases, give rise to the stalked ovules. The fruit is 

 normally 2-seeded, but may become 3-4-seeded by division of the 

 carpels, 1-seeded by abortion of one of the carpels. The normal female 

 flower of Salisburia is an axillary shoot, with two transversely placed 

 fertile carpels. In this respect Salisburia is more nearly allied to the 

 Ooniferae than to the Cycadese ; but properly constitutes a family by 

 itself, the Gingkoaceae. 



Fruit of Sambucus Ebulus.§ — Dr. P. Radulescu has investigated 

 the nature of the colouring matter of the juice of the berries of the 

 danewort, largely used for colouring red wines in Eoumania. Its chemical 

 and spectroscopic characters are given in detail. It possesses no injurious 

 properties. 



* Atti e Rend. Accad. Sci. Acireale, 1S99, 16 pp. 



t Coraptes Rendus, exxx. (1900) pp. 663-5. 



t Oesterr. Bot. Zeitschr., xlix. (1899) pp. 417-25 (1 pi.). 



§ Bull. Soc. Sci. Bucharest, viii. (1899) pp. 636-11. 



