Dkcemhkr, 191; 



KNO\VLI-:nGl-, 



473 



The effect of this would be more in evidence the nearer the 

 attracted body was to the sun ; it seems possible that the 

 anomalous motion of the perihelion of Mercury might thus be 

 explained. It will, of course, be understood that the screening 

 action must be extremely slight, and any eft'ects can only be 

 detected by the ijroatest care both in calculation and 

 observation. 



COMETS. — In addition to Gale's comet, mentioned last 

 month, two others have been discovered. The first, found by 

 M. Schaumasse at Nice, proved to be Tuttle"s comet, which 

 had returned two months earlier than was expected. No one 

 had computed the perturbations for this revolution, and 

 M. Fayet has since found that the action of Jupiter in 1901, 

 when there was a pretty near approach of the comet to it, 

 will fully explain the change of period. This has been the 

 shortest revolution of the comet since it was first seen, in 

 1790, and it is curious that the last revolution of Halley's 

 comet was also a shortest on record. The period of this 

 comet is thirteen and a half years, and six revolutions do not 

 differ much from seven of Jupiter, so that the perturbations 

 repeat themselves, and there is a wave in the periodic times, 

 similar to the one I showed for Encke's comet some time ago. 



Born-lly. 

 1912. Oct. 21-95 (;.M.T. 

 101° 31' 

 144 53 

 124 9 

 0-0457 



The following table gives the elements of Tattle's Comet by 

 MM. Favet and Schaumasse, and of Borrelly's Comet (c 1912) 

 by Dr. Kobold :— 



Tuttle. 



T 19I2,Oct. 28-4106 Paris M.T. 



w 206° 51' 29" 



9, 269 Si 57 



1 55 24 



log q 0-01191 



e 0-8183' 



Tuttle's Comet will be too far south for European observation 

 in December. 



Borrelly's Comet will be in R.A. 19" 58"", N. Dec. 3" 14' on 

 December 1st; daily motion +2" 24', South 45'. It will be 

 of the tenth magnitude. 



Gale's Comet may still be seen in the telescope. 

 Place on December 4th, R.A. le*" 34" 55'. N. Dec. 46° 56'. 



8th, R.A. 16" 40'" 25». N. Dec. 49° 50'. 



BOTANY. 



By Professor F. C.wers, D.Sc, F.L.S. 



BOTANY AT THE BRITISH ASSOCIATION.— The 

 Presidential Address given by Professor Keeble to Section K 

 (Botany! was exactly what might have been expected from 

 one who has shown in his publications how even the most 

 specialised of subjects may^ be made intelligible and fascinat- 

 ingly readable to the non-specialist, if presented in that lucid 

 style which is either a happy knack or the outcome of an 

 infinite capacity for taking pains. Professor Keeble's intro- 



ductory remarks were both witty .-md wise. He began by 

 comparing himself with Autolycus, as one who had worked on 

 the border-lines of several biological sciences, though readers 

 of his wonderful little book " Plant-animals " would certainly 

 not be inclined to consider the results of its author's brilliant 

 investigations as " unconsidered trifles." After discussing the 

 merits and drawbacks of the general and special methods for 

 a presidential address, the President compared the specialisa- 

 tion of science in our times with the versatility of the great 

 Victorian naturalists, and passed some searching criticisms on 

 our methods of University teaching in science. 



ANIMAL PARASITES OF PITCHER - PLANTS.— 

 Jensen {Ami. jard. bot. Buitenzorg, Suppl. 3, Part 2) has 

 described an interesting case of symbiosis or parasitism, 

 analogous to the presence of intestinal parasites in animals, 

 in the pitchers of Nepenthes. These pitchers are, as is well 

 known, filled with fluid containing ferments in which dead 

 insects are digested, but Jensen has found that several species 

 of fly larvae develop normally in this fluid. So abundant are 

 they that the author found them in every one of the hundreds 

 of pitchers he examined during several successive years in 

 Java. These dipterous larvae were reared, and six of the 

 seven discovered in this curious habitat were found to be new 

 species, belonging to three different families of Diptera. One 

 of the most remarkable characters of these larvae is their 

 power of " anti-fermentation," which appears to retard the 

 action of the ferments in the fluid filling the pitchers. This 

 retarding action was definitely proved by experiments, the 

 larvae being placed in solutions of pepsin and pancreatin. 

 Closely related larvae taken from neighbouring pools were 

 unable to live in the pitchers, hence the anti-ferment is to 

 be regarded as an adaptation to this symbiotic mode of life. 



ORCHIDS AND THEIR FUNGUS-GUESTS. — The 

 roots of various orchids contain a helpful fungus which 

 enables them to absorb food from decaying humus. Bernard 

 (Ann. Sci. Nat., Bot., IX., 14) has shown that small portions 

 cut from the bulbous parts of son;e orchids appear to have a 

 poisonous effect on the root-inhabiting fungus or mycorhiza of 

 the same plants. In cultures the fluid diffusing from the bulb 

 material killed the threads of the fungus. When heated to 

 55°C. the toxic properties of the bulb are destroyed, and this 

 with other data leads to the conclusion that the substance 

 acting as a fungicide is a ferment (enzyme). It .serves to 

 explain the fact that no endophytic fungi are found in the 

 bulbous portions of various orchids which contain fungus in 

 their roots, and also confirms Bernard's view that these orchids 

 tolerate the mycorhiza, though well able to defend themselves 

 against its complete invasion of their tissues. 



CHEMISTRY. 



By C. AiNswoRTH Mitchell, B.A. (Oxon.), FM.C. 



EFFECTS OF STERILISING SOIL. — A series of 

 instructive investigations upon the sterilisation of soil by 

 means of steam has recently been published. The principal 

 chemical changes that take place when the soil is subjected to 

 the action of steam under pressure arc described by Messrs. 

 Lathrop and Schreiner, in The Journal of tlie American 

 Chemical Society (1912, XXXIV, 1242). From their 

 experiments it appears that the proportion of substances 

 soluble in water is increased by the process, while the 

 acidity of the soil is also increased, even though ammonia 

 and allied compounds are simi.itaucously produced. Most 

 of the organic compounds that have been isolated from 

 ordinary soil also show an increase after the steaming, 

 nucleic acid being an exception. 



Products of the decomposition of nucleic acid and proteins 

 which are favourable to the growth of plants are formed in 

 the steaming process ; but there is also a simultaneous 



.\t these returns the comet was not seen : the values are calculated by Clausen. 

 t I have corrected this value to correspond with tlie actual period of the comet : the authors gave 0-8055. 



