AGEICULTUEAL BOTANY; 329 



to secure a maximum yield tl]rouf.'ti the solutiou of plant food in cultui'e 

 experiments. 



Some conditions for the formation of chlorophyll, B. L. Issatchenko {Izv. 

 Imp. St. Peterh. Bot. Sada (Bui. Jardin Imp. Bot. SI. Pctersh.). 9 {1909), ^'o. 5, 

 pp. 107-120). — The author has given a resume of his investisiations relating to 

 the conditions under which chlorophyll is formed. 



He has found that a temperature as low as — S° C. does not check the forma- 

 tion of chlorophyll and that pigment is rapidly formed at the low temperature, 

 illumination being the necessary condiiion for its formation. Chlorophyll, he 

 claims, is formed under anaerobic conditions, and atropiu, morphin, and other 

 poisonous substances do not retard its production. It is also formed in the [ires- 

 ence of vapors of formaldehyde or of chloroform, and this is believed to indi- 

 cate that si)ecific ferments liave no part in its production. Hydrogen i)eroxid 

 in a solution of 10 to 20 per cent checked the production of chlorophyll in etio- 

 lated leaves for 2 or 3 hours. After this time it was formed if the leaves were 

 placed in the light, but if k('])t in darkness protochlorophyll was produced. 



Phosphorus in relation to chlorophyll, V. Brdlik (Sitzbcr. E. Aknd. Wiss. 

 [Vienna], Math, ^aiul■tt■. KL, HI H908). Xo. 5-6, pp. ii29-5.'f6). — The author 

 states that not only does the physiological action indicate a close relation be- 

 tween phosphorus and chloi'ophyll in the plant cell, but alcoholic and benzol 

 extracts of green leaves show an inorganic phosphorus compound as well as col- 

 orless phosphatids, indicating that phosphorus plays a very important role in 

 chlorophyll formation. The phosphorus in the plant was found to occur not 

 only in combination with glycerin but also in other forms, and it is believed to 

 play as important a role in the physiological activity of the plant as magnesium 

 or potassium. 



The relation between the intensity of lig'ht and the duration of illumina- 

 tion to the response in oat seedlings, A. J. Blaalw {K. Ahad. WctcnscJt. 

 Amsterdam, I'roc. Sect. Sci.. 11 (1908-9), pt. 1, pp. 230-23-'/).— Experiments are 

 reported with etiolated seedlings of oats in which the phototropic response to 

 the intensity of light and the length of illumination was measured. Welsbach 

 burners, kept constant by means of a gas-pressure regulator, were used for 

 the weaker intensities, while for the greater light intensities electric arc 

 lamps together with condensers were employed. The periods of illumination 

 varied from 0.001 second to 13 hours, after which the plants were placed in 

 darkness, and examined for phototropic curvature after about 2 hours. 



The results show that a definite quantity of light is required to produce 

 reaction, the intensity being inversely proportional to the length of exposure. 

 For the production of phototropic curvature a definite quantity of radiant 

 energy is necessary, and whether this is supplied in a very short time or with 

 extreme slowness is a matter of indifference on the part of the plants. 



The biological significance of nectar in the flower, W. Burck (K. Alcad. 

 Weten.scti. Amsterdam, Proc. Sect. Sci., 11 (1908-9), pt. 2, pp. U5-'f.59).—A 

 study was made of the function of nectar in plants. 



The author holds that there is a connection between the secretion of water 

 and nectar in plants and that by the nectar secretion the sex organs in the 

 flowers are protected. He has found that the nectar serves to keep the flower 

 moist during the flowering period, thus aiding in the pollination. A number of 

 so-called nectarless plants were investigated, and it was found that these secrete 

 wax or mucilage, the biological significance of which is similar to that attrib- 

 uted to nectar. 



The influence of air moisture on the duration of vitality of pollen. M. 

 Pfundt (Jahrb. Wiss. Bot. [Pringsheitn], Jf7 (1909), Ao. 1, pp. l--iO, dgm. 1).— 



