834 SUMMARY OF CURRENT RESEARCHES RELATING TO 



wanting in the stem ; e. g. woody fibres (Thymus vulgaris) ; tlie special 

 reticulate cells {Acacia cultriformis). These modifications sometimes 

 correspond to the size of the floral organs, or to the size or con- 

 sistency of the fruit ; but most frequently they can only be connected 

 with the function of those organs. In fact, on comparing the 

 peduncles with the petioles, it is seen that the most marked and 

 constant difference which distinguishes them is in the number and 

 size of the large vessels of the wood ; few and small in the former, 

 numerous and large in the latter. 



From the point of view of sexuality, the influence of the flower on 

 the organization of the peduncles sometimes expresses itself in well- 

 defined characters. Thus the peduncles of the female flowers of 

 certain monoecious species always possess a thicker bark, and a better 

 organized woody ring furnished with larger if not more numerous 

 vessels, than the peduncles of the male flowers [Castanea vulgaris, 

 Juglans regia, &c.) In short, the floral axes present modifications, 

 more or less marked, which express in some sort the influence which 

 the production of flowers exercises, and gives us, so to speak, the 

 measure of its value. This influence may be nothing or at least may 

 appear to be such. Often it does not extend beyond the immediate 

 supports of the flower, or at least of the various members of the inflo- 

 rescence (Pavia rubra, Vitis vinifera, &c.). And lastly, in some plants 

 it makes itself felt as far as the branches which give rise to the floral 

 axes, so as to provoke in them either a partial modification (Ribes 

 malvaceum), or a complete differentiation (fruit-bearing branches of the 

 pear and apple, of Salisburia, &c.). 



Wolffia microscopica.* — Herr F. Hegelmaier describes the struc- 

 ture and anatomy of this previously little-known species, the smallest 

 of flowering plants, from India. Its most striking external peculiarity 

 is the rhizoid or " radicula " of Griffith, a comparatively large conical 

 protuberance from the lower surface of the plant, somewhat nearer to 

 the base than the apex of the shoot, the purpose of which appears to 

 be to enable the plant to float in a horizontal position. The author 

 suggests that in the allied genus Wolffiella we may have a true 

 example of apogamy, hitherto unknown in flowering plants, a con- 

 tinual non-sexual reproduction from generation to generation, with- 

 out seeds being ever produced. 



j8. Physiology, t 



Fertilization of Asclepias Cornuti.J— Mr. T. H. Corry describes 

 in great detail the structure and development of the gynostemium and 

 the mode of fertilization in this plant. Pollination takes place 

 entirely by the agency of insects, and only in fine weather ; and the 

 author states that, as far as his observation goes, the flowers are 

 absolutely sterile when pollinated artificially from poUinia extracted 

 either from the same flower or from another of the same age. This is 



* Bot. Ztg., xliii. (1885) pp. 241-9. 



t This subdivision contains (1) Reproduction (inchiding the formation of the 

 Embryo and accompanying processes) ; (2) Germination ; (3) Growth ; (4) Respira- 

 tion ; (5) Movement ; and (6) Chemical processes (including Fermentation). 



t Trans. Linn. Soc. Loud.— Bot., ii. (1884) pp. 173-207 (3 pis.). 



