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NATURE 



[November io, 1910 



I 



BOTAW AT THE BRITISH ASSOCIATION. 



The President's Address. 



N accordance with the custom that is growing up of 

 arranging for a minimum of clashing between the 

 various presidential addresses, Prof. Trail delivered his 

 address (which was printed in full in Nature of October 0) 

 at 12 noon on Thursday, September i. The address 

 dealt with the subject of field botany, and the president 

 particularly urged the need for the preparation of a really 

 great national flora. .As a direct outcome of the address, 

 a corhmittee was subsequently appointed, with Dr. Trail 

 as chairman, to consider what steps should be taken 

 towards organising and preparing the materials for such 

 a flora. 



.Vs regards the rest of the proceedings, the outstanding 

 features of. the Sheffield meeting were the sittings devoted 

 respectivelv to physiology, cytology, and morphology. 

 Judged by the keenness of the discussions and the numbers 

 attending the section, the meeting must be pronounced to 

 have been distinctly better than the average. It will be 

 convenient to deal first with the subject of physiology. 



Physiology. 



On Monday morning, September 5, there was a joint 

 sitting of the botanists, chemists, and physiologists in the 

 meeting-room of Section K, the subject being the bio- 

 chemistry of respiration. A report of this discussion will 

 be found in the account of the proceedings of Section I 

 (p. 26), so it is unnecessary here to do more than men- 

 tion the botanical contributions to the discussion. Dr. 

 F. F. Blackman, who opened the subject, by way of 

 introduction outlined our present knowledge of the re- 

 spiration of plants in respect to : — (i) the nature of the 

 reaction (or reactions) which constitutes respiration ; 

 (2) the physical chemistry of the respiration reaction : and 

 ^3) the influence of protoplasm upon the progress of the 

 reaction. Mr. D. Thoday dealt with the effect of chloro- 

 form on the respiration of plants. 



Tuesday morning, and to some extent Wednesday, were 

 also devoted to physiological papers. Mr. S. Mangham 

 read an interesting paper on the paths of translocation of 

 sugars from green leaves. Using Senft's method of test- 

 ing for sugars by the precipitation of osazones, the author 

 was able to obtain definite evidence that the sieve-tubes 

 (and not the parenchymatous vein sheaths) provide the 

 main paths for the translocation of free sugars from the 

 lamina of the leaf. He was thus able to confirm Czapek's 

 theory, which had been disputed by Haberlandt and others. 

 Mr. D. Thoday followed, and discussed assimilation and 

 translocation under natural conditions. His experiments 

 show that in detached leaves the increase of dry weight, 

 due to assimilation, is surprisingly small in bright diffuse 

 light as compared with bright sunlight. Leaves still 

 attached to the plant show a smaller rate of increase than 

 detached leaves ; this is probably largely due to trans- 

 location. Dr. F. Darwin demonstrated a new method of 

 observing in living leaves, while still attached to the 

 plant, the degree to which the stomatal apertures are 

 open or closed. The instrument (which he calls a poro- 

 ineter) consists of a small glass chamber cemented on to 

 the stomatal surface of a leaf, and connected with a 

 suction tube and manometer. By diminishing the air- 

 pressure in the chamber a flow of air through the stomata 

 is induced, the rate of flow indicating the condition of 

 the stomatal apertures. Dr. Darwin then discussed some 

 actual results obtained by the porometer. On comparing 

 the readings of the latter with the loss of weight by 

 transpiration, it was found that the two curves rise and 

 fall together, but the transpiration readings have a much 

 smaller range than those of the porometer. This is 

 perhaps what might have been expected, taking into 

 account Dr. Horace Brown's work on diffusion. 



Miss N. Darwin and Dr. F. F. Blackman contributed 

 a paper on germination conditions and the vitality of 

 seeds. If the vitality of seeds is lowered by exposure to, 

 e.g., high temperatures, they do not germinate well, and 

 become more sensitive to any unfavourable modification 

 of the environment. Failure to germinate when too little 

 water is present is due to purely physical causes, while 



NO. 214I, VOL. 85] 



the injurious effects of excess of water are due to the 

 water acting as an o.xygen excluder. Mr. A. S. Home 

 next discussed the absorption of water by various legu- 

 minous seeds. Prof. Bottomley showed that the Cyano- 

 phyceae endophytic in the apogeotropic roots of cycads 

 and in the cavities of .Azolla and Anthoceros are invariably 

 accompanied by nitrogen-fixing bacteria. He suggested 

 that this may really be a symbiotic association of the 

 algae and the bacteria. 



Ecology. 



In contrast to the Winnipeg meeting, ecology was re- 

 presented this year by only two papers. Mr. J. H. 

 Priestley gave an account of the distribution of halophyte;, 

 on the Severn shore. In this district the halophytes 

 exhibit three well-marked zones : — (i) the low-lying 

 Salicornia zone ; (2) the Sclerochloa and .Aster zone ; and 

 (3) the rarelv submerged Junciis Gerardi and Festuca 

 rubra zone. Apparent anomalies of distribution are prob- 

 abl)' referable to differences of drainage and salinity. Mr. 

 M. Wilson discussed plant distribution in the woods of 

 north-east Kent. 



Cytological Papers, <5^'C. 



Friday morning was occupied with papers dealing with 

 cytology and heredity, the first two being taken jointly 

 with .Section D (Zoology). In a paper entitled " The 

 New Force, Mitokinetism," Prof. Marcus Hartog further 

 developed his views on the formation of the spindle and 

 other structures observed during karyokinesis. Discuss- 

 ing the various theories put forward. Prof. Hartog con- 

 tended that neither diffusion currents on one hand, 

 nor electrolytic or electrostatic force or magnetism on the 

 other, are sufficient to account for the formation of the 

 mitotic spindle. As an alternative the author postulates 

 the existence of a new force, which he terms "mito- 

 kinetism," and which, so far, is unknown outside the 

 living cell. Dr. E. Hindle followed with an account of 

 artificial parthenogenesis in the eggs of a sea-urchin 

 (Strongylocentrotus purpuratus). The author described the 

 process of artificial fertilisation in these eggs by treatment 

 with a monobasic fatty acid, and subsequently with hyper- 

 tonic salt solution. The cytological changes undergone 

 were carefully described, including the formation of an 

 artificial fertilisation membrane and the various nuclear 

 changes. Under suitable conditions free-swimming larvae 

 were produced. These, though their dividing nuclei con- 

 tained only the reduced number of chromosomes, were 

 identical in form and behaviour with those developed from 

 normallv fertilised eggs. This concluded the joint sitting 

 of Sections D and K, and the remaining papers were com- 

 municated to Section K alone. 



The next two papers dealt with the behaviour of the 

 chromosomes during mitosis, and particularly with respect 

 to the stage at which longitudinal fission is initiated. 

 Prof. Farmer and Miss Digby found in Galtonia that 

 during the archesporlal divisions the longitudinal fission 

 begins by a condensation of the chromatin on the edges 

 of the chromosomes during the telophase of the preceding 

 division, and the duplicate character can thus be detected 

 verv early. Similarly, in the heterotype division of 

 mitosis, the longitudinal fission is prepared for, as in the 

 somatic mitoses, during the telophase of the last arche- 

 sporlal division. Dr. Fraser and Mr. Snell obtained very 

 similar results in Vicia faba. They found that the 

 chromosomes which are separated from each other in any 

 given division are the product of a longitudinal fission 

 which is initiated in the preceding telophase. This was 

 stated to be the case in both the sporophyte_ and gameto- 

 phvte generations, the resting chromosomes in both cases 

 exhibiting a double structure. Prof. V. H. Blackman, in 

 a very interesting short paper, described the vermiform 

 male nuclei of Lilium. The author brought forward 

 evidence that, although purely nuclear in structure and 

 possessing no cilia, these structures are capable of active 

 movement. It seems probable that the activity of these 

 nuclei, and not the streaming movements of the surrounds 

 ing cytoplasm, is responsible for their entrance into the 

 ovum and passage to the polar nuclei. 



The remaining two papers taken on Friday dealt with 

 problems of heredity. Mr: R. P. Gregory offered sonie 

 further observations on inheritance in Primula sinensis. 



