668 StTMlTAET OF CUREENT EESEAECHES RELATING TO 



(2) Nutrition and Growtli (including Movements of Fluids). 



Development of Animal Plants.* — M. H. Juraelle describes the 

 variatioDS whicli the different members of an annual plant undergo 

 according to their age, and to the external conditions to which they are 

 subjected. From germination to maturity five principal periods may be 

 distinguished. In the first, or genniuating period, there is a simple 

 migration of matter from the cotyledons towards the hypocotyledonary 

 parts, and the plant not only does not ass'milate, but loses some of its 

 dry weight by chemical transformations. In the second period assimila- 

 tion commences. The cotyledons lose a further portion of their sub- 

 stances to the hypocotyledonary, and also to the epicotyledonary parts 

 which now begin to develope. The third period is marked by the dis- 

 appearance of the cotyledons, and there is a rapid transportation of 

 substance from the hypocotyledonary axis towards the summit of the 

 plant. In the fourth j)eriod the flowers appear, and a fresh migration 

 of matter takes place towards the summit of the plant. The fifth period 

 commences after flowering. There is a considerable increase in dry 

 weight in the root, stem, and leaves ; and the absorption of mineral 

 matter is very active. The quantity of water follows less rapidly and 

 in different proportions these variations of dry substance. In the 

 cotyledons, on the contrary, it tends to augment while the dry material 

 diminishes. 



Influence of External Agents on the Polarity and Dorsiventral 



Structure of Plants.l — M. Kolderup Eosenvinge in the first place de- 

 scribes various experiments made with the spores of the Fucacefe, in 

 order to determine the influence of external agents on polarity. The 

 following are the most important conclusions : — (1) The j)olarity of 

 the spores which germinated (that is, the determination of the point 

 where the rhizoids and the apical point appeared) can be determined by 

 diverse external agencies ; (2) Light may influence the orientation of 

 the first septum ; (3) Light determined the polarity of the plants in all 

 the species studied except Fucus serratus. The sensibility to light was 

 greatest in Pelvetia canalkulata ; (4) Gravitation had no influence on 

 the polarity of the plants ; (5) Contact with a solid body had no 

 influence on the polarity of the plants ; (6) A difference in the quantity 

 of oxygen on the different sides of the spores affected the polarity, 

 rhizoids forming on the side where the oxygen was most feeble ; (7) In 

 all the species the polarity could be determined exclusively by internal 

 causes, which seemed independent of the orientation of the oosphere in 

 the oogone. 



In the second part of the paper the author discusses the dorsiventral 

 structure of plants. It is well known that dorsiventral organs are 

 ordinarily plagiotropic ; nevertheless shoots have been found in Yicia 

 Faba and several species of Begonia, which grow vertically, although 

 they have a pronounced dorsiventral structure. Centradenia floribunda 

 furnishes an example of a dorsiventral structure which is produced by an 

 external influence, and which can be reversed by inverse action of the 

 cause which produced it. In none of the other plants studied could the 



* Eev. Gen. de Bot. (Bonnier), i. (1889} pp. 101-22, 195-211, 258-79,318-29; 

 and Bull. Soc. Bot. France, xsxvi. (1889) pp. 72-6. 



t Eev. Gen. de Bot. (Bonnier), i. (1889) pp. 53-63, 123-35, 170-4, 244-55, 

 304-17 (19 fis:?.). 



