BOTANY. fi51 



In the second part of the report the investigationK arc confined to succulent iilants. 

 These liave long l)een known to lie peculiar in their absorption and excretion of 

 oxygen and i-arbon dioxid gas, as well as in their acidity. The author has shown 

 that the acidity of tliese plants, -which is chiefly due to malic acid, increases consid- 

 erably during darkness. In a leaf partly exposed to full sunlight the acid content 

 is distinctly greater in the shaded parts and less in the exposed parts. This disap- 

 pearance of acids in succulent plants is said to be due not to their fixation, but to 

 the processes of respiration and assimilation. The transpiration of the succulents 

 studied was influenced more by the salts present in the different organs of the plants 

 than by their acid content. 



The significance of ethereal oils in xerophytes, C. Detto {Fiord, 92 (1903), 

 pp. 147-i:)9,fi<i^. 7; ah-'i. i)>. Jnur. Ixoij. ITort. Sac [Lovdon], 28 {1903), No. 1-2, pp. 250, 

 251). — The author has examined the functions of ethereal oils in their significance 

 toward desert 2>lants. The theory of Tyndall that they serve to check excessive 

 heating by the opacity of their vapor to ultra-red rays is held to be improbable. 

 Dixon's theory that the function of essential oils is to check transpiration was exam- 

 ined and found to depend on the presence of these oils in the vapor. The author 

 regards the function as protective against many animals, such as mollusks, herbivo- 

 rous mammals, etc., and justifies his view by a careful series of experiments. 



Carbonic acid assimilation in submerged plants, O. Treboux (F/oro, 92 ( 1903), 

 pp. 77-97; uli-^. in Jour. Boi/. Hurt. Soi: [Londou], 2S {1903), No. i-^, p. ^-55).— Experi- 

 ments are reported on Elodea in a dark room illuminated l)y an incandescent lamp. 

 Various substances were added to the water and the rate of assimilation estimated 

 b}' counting the gas bubbles given off in 5 minutes. 



Asgimilation was found to be reduced by the addition of neutral salts, while salts 

 of the heavy metals, alkaloids, and ansesthetics, which in minute jiroportions increase 

 respiration, had no effect on assimilation. Chloroform was found to arrest assimila- 

 tion temporarily. All acids when sufficiently dilute not to be harmful increased 

 assimilation. Sufficiently dilute formaldehyde was indifferent to the rate of assimi- 

 lation, and neither in the presence of light nor in darkness was there any additional 

 starch formed from it. In stronger solutions formaldehyde was found to be injurious. 



Growth without oxygen, A. J. Nabokicii {Bot. Ccnthl., Beihefte, 13 {1902), No. 

 3, pp. 272-33Q; ahs. in Jovr. Roy. Hort. Soc. [London}, 28 {1903), No. 1-2, p. 264).— 

 A report is given of experiments in growing sunfloMer hypocotyls in flasks which had 

 been exhausted by an air pump and then sealed. The investigations showed that a 

 distinct elongation is perceptible in the absence of oxygen, and that practically no 

 effect is produced by traces of oxygen where the amount present is less than 0.06 

 per cent. 



The effects of temperature on the individuality and character of the mother plant, 

 of the duration of the experiments, and of the use of sugar solutions or water in the 

 experiments were investigated. It was found t-hat when seeds were germinated in 

 an atmosphere dejirived of oxygen there was a reduction tif nitric acid, although bac- 

 teria were absent from the substrata and from the seeds. The point of interest in 

 the paper is that the anaerobic life followed by many bacteria can be adopted by the 

 cells of higher plants under certain conditions. 



The effect of the temperature of the soil on the growth of roots, P. 

 Kossovicn {Zhur. Opui/n. Aijron. [Jour. Expt. Landu'.~\, 4 {1903), No. 4, pp- 389- 

 399). — The experiments reported upon were carried out in vessels having 3 zinc 

 walls and 1 of glass, permitting the examination of the root systems from time to 

 time. Each vessel received the same amount of soil and fertilizer, and the humidity 

 was maintained at 27.3 per cent of the dry soil. 



'ihe plants used in the experiments were oats, mustard, and liax; and the differ- 

 ent vessels were kept throughout the growing season at different temperatures liy 

 placing the vessels in zinc boxes sunk in the ground and the temperature regulated 



