462 



KNOWLEDGE. 



December, 1913. 



larger, and the degree of compression very much slighter, than 

 we are apt to imagine from their telescopic aspect. 



The nebulae, on the other hand, show a decided avoidance 

 of the Milky Way and an aggregation towards its poles, 

 especially the northern one in Coma Berenices. He has 

 divided the nebulae into various classes according to size, 

 shape, and brightness, but the same general arrangement 

 persists. He has not grouped them according to spectral 

 type (the distinction between "white" and "green" nebulae), 

 though this difference is more significant than the others. It 

 has been suggested that the paucity of nebulae along the 

 galaxy arises from the brightness of the sky background, and 

 the consequent difficulty of detecting faint nebulous objects. 

 However, even the bright nebulae cluster very definitely round 

 the Coma Berenices pole. There is no such marked aggrega- 

 tion of them at the opposite pole. 



On the whole it looks as if the Galaxy had some influence 

 on the distribution of nebulae ; if so, the greater part of them 

 belong to our own stellar system, and are not external 

 universes. This is also supported by the comparatively small 

 radial velocity indicated by those whose spectra have been 

 carefully observed. We should expect independent universes 

 to have considerable motion relatively to each other, and so to 

 show large radial velocities. Those actually found are of the 

 same order of magnitude as those of the stars. 



BOTANY. 



By Professor F. Cavers, D.Sc, F.L.S 



BOTANY AT THE BRITISH ASSOCIATION 



{continued). — Apart from the Presidential Address given by 

 Miss Sargant, the only notable paper of wide interest was that 

 by Professor Reinke, " On the Nature of Life." The veteran 

 Kiel botanist protested against the view that life can be 

 interpreted merely mechanically, and urged that the greater 

 the progress in experimental physiology, the better we learn to 

 use our knowledge of non-living matter for the explanation of 

 the processes of life, the more we understand that a complete 

 physico-chemical analysis is impossible for any important life 

 process. Behind all the physico-chemical facts ascertained 

 by physiological studies there hides an unknown factor, " an 

 * not to be solved by levers and screws and chemical 

 reagents." He maintained that although the laws of energy 

 are valid in the organism as well as in unorganised nature, 

 life being based on transformations of energy or "elementary 

 processes," these processes are not thrown together without 

 order in the living body, but are united by an invisible chain 

 which maintains order among the elementary processes and 

 represents the true difference between life and any event in 

 lifeless nature. This " life principle " is, unlike the single 

 elementary processes, inaccessible to physiological analysis ; 

 it is " no force or power, it is a principle of succession, of 

 order, of regulation, of harmony." 



An interesting " semi-popular address " was given by 

 Professor W. H. Lang on epiphyllous plants — chiefly algae, 

 lichens, and liverworts — which grow in a non-parasitic manner 

 on the foliage of trees in very damp tropical forests. He 

 pointed out the prevalence in such forms of an efficient means 

 of attachment to the surface of the leaf, and laid stress upon 

 the occurrence of flat disc-like early stages in the germination 

 of the spores of epiphyllous liverworts as an adaptation to this 

 mode of life. 



Among various other contributions on the morphology and 

 biology of cryptogams the following may be mentioned. 

 Professor West read two papers dealing with his observations 

 on the genus Microspora and on Zygnema ericetorutn : in 

 the former he pointed out that the isolation of Microspora in 

 a special order (Microsporales) of the Green Algae should be 

 given up. Dr. Darbishire described the development of the 

 apothecium in the lichen Peltigera, in which male organs 

 (spermatia) are very rare, though fruits are formed abundantly, 

 probably by apogamy ; no coiled carpogonia can be made out, 

 but there are deeply staining cells which form part of a connected 



system of branched hyphae proceeding from medulla to cortex, 

 becoming multinucleate by nuclear divisions in the cells 

 and (after producing functionless trichogynes which force 

 their way through the cortex) giving rise to large cells 

 (" ascogonia ") from which the asci derive their paired female 

 nuclei. Miss E. M. Poulton described the structure and life 

 history of an aquatic lichen, Verrucaria margaracea. In an 

 interesting paper, illustrated by very fine lantern slides, 

 Professor Buller described the structure of the gills in 

 the toadstool genus Coprinus, with special reference to the 

 beautiful adaptations shown by the basidia of varying lengths, 

 bearing the spores at different levels, and thus ensuring the 

 liberation of spores in the most efficient manner. The same 

 genus was dealt with by M. L. Baden, who found that, after 

 encountering great difficulty in germinating the spores of 

 Coprinus sterquilinus on ordinary media, vigorous germina- 

 tion occurred in media containing abundant bacteria, leading 

 to the conclusion that in some way the bacteria are of benefit 

 to the spores and to the mycelium formed by theirgermination — 

 possibly by producing substances which soften the spore coat, 

 or by removing any by-products of the fungus which may 

 hinder germination. The apple-canker fungus, Nectria 

 ditissitna, was described by S. P. Wiltshire, who found that 

 this fungus, which is a genuine wound parasite, can only 

 attack trees when the injury is deep enough for the fungus to 

 reach the wood, and that in nature the chief means of inocula- 

 tion are injuries made by frost and by the woolly aphis 

 (Schizoneura lanigera), in both cases the bark being burst 

 by the swelling of the various tissues ; the reactions of the 

 host against the disease are the formation of phellogen at the 

 limits of the infected region in the cortex, of abnormal wood 

 similar in structure to the medullary rays, and of wound gum 

 in the wood vessels. Miss M. Hume described the structure 

 of the leptoids, or " sieve-tubes," of the moss genus Poly- 

 trichum, pointing out that these cells have a nucleus though 

 never containing starch grains or large oil drops like the other 

 living cells of the moss stem. Direct experiments indicate that 

 the conducting function of the leptoids is probably confined 

 to albuminous materials and is not concerned with carbo- 

 hydrates, the latter being possibly conveyed by the hydroids 

 which probably have not a purely water-conducting function. 



Dr. R. R. Gates presented and discussed certain evidences 

 to show that mutation and Mendelian splitting are different 

 processes. Results have been obtained showing that some 

 at least of the mutations of Oenothera are not due to 

 recombinations of Mendelian characters, as some writers have 

 assumed, but to irregularities in the reducing nuclear division 

 (" meiosis ") which lead to changes in nuclear structure. The 

 cases of O. lata and O. semilata alone were referred to in 

 this paper, because they offer a means of differentiating 

 between characters which are inherited from the parents and 

 those which arise as a result of unequal or irregular distribu- 

 tion of the chromosomes during meiosis : these mutant forms 

 have fifteen chromosomes instead of fourteen, and the same is 

 true of all individuals possessing the foliage and habit of lata 

 or semilata, even when these characters are associated with 

 others derived by inheritance from their parental forms. 

 Such cases show definitely that mutation is a process which is 

 independent of the recombinations of characters such as 

 occur in hybrids. The source of the fifteen chromosomes was 

 shown some years ago to lie in occasional irregularities in the 

 distribution of the chromosomes during reduction ; two pollen 

 grains of a pollen tetrad receive eight chromosomes, and the 

 other two receive six, and when an egg having seven chromo- 

 somes is fertilised by a male cell from a pollen grain 

 with eight, the resulting individual will have fifteen 

 chromosomes and the foliage of lata or semilata. The extra 

 chromosome, which is a triplicate of a pair already 

 present, is thus associated with the development of certain 

 foliage characters in Oenothera in the same way that the 

 accessory chromosome, when present in duplicate, is, in 

 certain insects, associated with the development of female 

 sex characters. This is apparently the first case in plants in 

 which a definite relation has been shown to exist between a 

 chromosome and particular external characters. 



Physiology was represented mainly by a joint discussion 



