ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 485 



J3. Physiology. "^ 



Development of the Endosperm in Hordeum.t— In the formation 

 of the endosperm in barley, M. W. Johannsen finds that the connecting 

 fibres between the newly developed daughter-nuclei have not the 

 usual barrel-shaped figure, but run parallel to one another near to 

 the nucleus. He was not able to follow the division of the central 

 nucleus in the embryo-sac, 



The so-called "gluten-cells" (Kleher-zellen) of the endosperm, 

 which contain oil but no starch, he considers have been unfortunately 

 so called, since they have nothing to do actually with the gluten of 

 the grain. The three outer layers of the endosperm contain protein- 

 grains, with but little power of resistance, lying in a protoplasmic 

 matrix abounding in oil. 



The author describes the method by which he prevents the 

 entrance of air into the endosperm in making sections of the grain. 



Influence of Light and Heat on Plant Development.^— Dr. H. 

 Hellriegel finds that the temperature during which plant life pro- 

 ceeds is confined within narrow boundaries, there being a limit for 

 each plant. Near the lowest limit the growth is very slow, but as 

 temperature rises life becomes more energetic, until a certain tem- 

 perature is reached, when the life is most energetic ; this temperature 

 is the " optimum," and does not of necessity coincide with the highest 

 temperature at which life ceases. As a rule the optimum tempera- 

 ture lies between 20° and 40° C. ; at 50° life is estinguished. In an 

 analogous manner, light or darkness produces a definite effect ; for 

 although germination takes place better in darkness, no plant can 

 thrive without light, the plant is bleached, leaves and stems become 

 abnormal, and the weight of dry matter diminishes. In subdued 

 light, assimilation proceeds but slowly, but is more rapid as the 

 intensity of light increases ; the maximum of rapidity, however, is 

 not coincident with the maximum intensity of light. The combina- 

 tion of warmth, light, and moisture forms a very important factor 

 in the fertility of the plant, and in many cases it is of more import- 

 ance than manui'ing, &c. The lowest limit of temperature at which 

 the majority of seeds germinate is 4-5° 0., but a few can germinate 

 at zero. 



Experiments are detailed which were made on various seeds, some 

 in soil kept at different temperatures for 35-60 days. 



The results of Hellriegel's further researches § are as follows : — 

 As it was thought impossible that plants growing in glass-houses 

 could obtain light of an intensity equal to that which they would 



* This subdivision contains (1 ) Reproduction (including the formation of the 

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

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



t Meddel. Carlsberg Lab., ii. (1884) (3 pis.). See Bot. Oentralbl., sxi. (1885) 

 p. 44. 



t Bied. Centr., 1884, pp. 123-6. Of. Journ. Chem, Soc— Abstr,, xlvi. (1884) 

 pp. 855-6. 



§ Bied. Centr., 1884, pp. 240-83. Cf. Journ. Chem. Soc— Abstr., xlvi. (1884) 

 j)p. 1206-7. 



