184 SUMMARY OF CUERENT RESEARCHES RELATING TO 



short-styled flowers, shows that the specialisation of two sorts of female 

 flowers is not complete, for the short-styled flowers are just as well fitted 

 for producing seed as for nourishing Blastaphaga. The plant is monoe- 

 cious with normally constituted male and female flowers. The summer 

 figs inclose male flowers, which produce pollen, and female flowers, 

 which nourish Blastaphaga ; the latter passes out and carries either 

 pollen or its own eggs to flowers inclosed in figs of the second or third 

 crop, but the flowers which form seeds are of exactly the same constitu- 

 tion as those which develop galls. 



Pollen-grain.*. — Germano Vert calls attention to the similarity 

 existing between pollen-grains and spores. After briefly noting the 

 difl'erences between multiplication and sexual reproduction, he points 

 out that the methods of fertilisation which obtain among higher 

 plants are quite different from what might be expected from a 

 study of lower forms. The author makes a comparison between the 

 structure and appearance of the spore and the pollen-grain, and notes 

 the similarity in the manner of germination, and the growth of the 

 hypha from the spore and the tube from the pollen-grain. Finally, 

 he shows that the difliculty encountered by the male element in reaching 

 the female, has been met by utilising an element possessed by the vege- 

 tative portion of the organism, \'iz. the spore. 



Physiology. 

 Nutrition and Growth. 



Respiration of Seeds in Latent Condition. f — P. Becquerel has 

 made two series of experiments upon the respiration of seeds. In the 

 first he used seeds in their natural dry state ; in the second he used seeds 

 which had undergone the maximum amount of desiccation. The 

 author finds that, generally, when left for a sufficiently long time, seeds 

 do give off a trace of CO2 and absorb a small amount of oxygen, when 

 placed in the dark in their naturally dry state. Light greatly increases 

 this gaseous exchange, owing to its power of promoting oxidation. 



The teguments of the seed play a most important part ; in some 

 cases, e.g. Ricinus, the gaseous exchange of the teguments was greater 

 than that of the seeds from which they had been removed. Lastly, 

 dehydration of the seeds is an important factor ; in same cases the 

 absence of moisture entirely prevents gaseous exchange. 



Increase in Growth of Trees.| — Fran9ois Koressi has studied the 

 laws of the increase in volume of trees, and finds that this increase is a 

 linear function of the time of growth. The increase in volume is pro- 

 portional to the cube of the time, under constant biologic conditions, 

 and maybe represented by y= M^^ Owing to the variation of biologic 

 conditions, M will not be a constant, but will itself be a function of the 

 time. The function Mt is subject to two kinds of variations, viz. 

 (1) fluctuation due to variation in climatic conditions ; (2) decrease due 

 to the constant pressure exerted by the exterior annual rings upon the 

 internal ones. 



* Comptes Rendus, cxliii. (1906) pp. 977-9. t Tom. cit., pp. 974-7. 



X Op. cit, cxlii. (1906) pp. 1430-2. 



