472 



NATURE 



[December 23, 19 15 



correct. When the stronger light falls upon one side 

 of the leaf-stalk, those cells on the side which is 

 more illuminated are stimulated to activity to a greater 

 extent than those on the less illuminated side, and the 

 stimulus is transmitted to the motor region. Inasmuch 

 as this stimulus is due to physico-chemical changes set 

 ■up in the cells nearest to the light, the plant may be 

 said to perceive a difference in the effects produced 

 by the light on the two sides— that is, it is able to 

 compare the two intensities. As soon, however, as the 

 leaf reaches its right position, the apex of the stalk is 

 illuminated more or less equally on all sides, and as 

 the physico-chemical changes in the cells may now be 

 considered to be more or less equal, no further stimulus 

 will be transmitted, or, if so, will be transmitted 

 equally all round the stalk, and no curvature in either 

 direction will take place. The leaf now being placed 

 in a definite position with reference to the direction 

 of the light rays, it would seem quite justifiable to 

 conclude that the plant is capable of perceiving the 

 direction of the rays of light. 



_ But the leaf is also capable of distinguishing between 

 light of different wave-lengths. Notwithstanding the 

 fact that rays of light both at the red end and at the 

 blue end of the spectrum are absorbed, the plant 

 responds phototropically mainly to the rays at the 

 blue end of the spectrum, very slightly, possibly, in 

 some cases to the red rays. This has been demon- 

 strated by keeping plants behind different coloured 

 light filters, and also in different parts of the spectrum. 

 That this power is localised in the percipient region 

 at the apex of the leaf-stalk can be very easily proved 

 by exposing this percipient region to rays of 'the blue 

 or red colour. The filters prepared and spectro- 

 scopically examined by Messrs. Wratten and Wain- 

 wright can be used for this purpose. Experiments 

 were made with blue, green, and red filters. A strong 

 curvature took place under the influence of the blue 

 rays, but no curvature under the influence of the green 

 or red rays, even when the exposure was continued 

 for more than a week. 



Here we have to do, therefore, with the quality as 

 well as with the intensity and direction of the light 

 rays, and the fact that the plant is more sensitive 

 heliotropically to the shorter and more frequent vibra- 

 tions at the blue end of the spectrum than to the 

 longer and less frequent vibrations at the red end, 

 indicates that it cannot merely be the direction of the 

 light rays that is perceived. Moreover, we must 

 remember that the plant does not respond directly to 

 the action of light, but to the physico-chemical 

 changes that take place in the photo-sensitive cells 

 of the percipient region. We ourselves perceive the 

 light because the brain is able to translate into sense 

 impressions the physico-chemical changes which take 

 place in the elements of the retina. The plant per- 

 ceives the light because it is able to translate into 

 a motor response the physico-chemical changes taking 

 place in the photo-sensitive cells of the perceptive 

 region. 



We may Imagine that in the plant the action is as 

 follows : The light is absorbed by, and excites, certain 

 photo-active substances in the cells of the sensitive 

 region. A stimulus is thus set up which is conveyed 

 through the cytoplasmic fibrils of the protoplasts to 

 the_ motor region. A further Impulse Is then set up 

 which acts upon the cells in the motor region, by 

 which it is probable that changes In the permeability 

 of the protoplasts are effected; the turgor conditions 

 of the cells are thereby differentially altered, and the 

 result Is a motor response. We have here, in fact, a 

 very simple type of reflex act taking place through 

 the agency not of highly specialised nerve-cells, but 

 of ordinary protoplasm and of the delicate proto- 

 plasmic fibrils which extend from one cell to another. 

 NO. 2408, VOL. 96] 



UNIVERSITY AND EDUCATIONAL 

 INTELLIGENCE. 

 Oxford. — Prof. R. B. Clifton, who lately retired 

 from the professorship of experimental philosophy at 

 the end of his fiftieth year of service, has been elected 

 to an honorary fellowship at Wadham College. He 

 has been connected with that college ever since his 

 appointment in 1865, and was an ordinary fellow for 

 the thirty-two years previous to his retirement. 



The Secretary of State for India has appointed Mr. 

 K. Zachariah to be professor of political economy and 

 political philosophy at Presidency College, Calcutta ; 

 and Mr. W. A. Jenkins to be professor of physics at 

 the Dacca College. 



We learn from the issue of Science for December 3 

 that objections have been filed to the will of the late 

 Mr. Amos F. Eno, who bequeathed a large sum to 

 public purposes and made Columbia University his 

 residuary legatee. It Is said that under the will 

 Columbia University would receive 6oo,oooZ. or more. 

 Our contemporary also states that a bequest of io,oooZ. 

 has been made to Cornell University by Mrs. Sarah 

 M. Sage to promote the advancement of medical 

 science by the prosecution of research at Ithaca. 



We have received from Washington a copy of a 

 timely volume prepared by Mr. S. P. Capen, specialist 

 in higher education of the United States Bureau of 

 Education, entitled "Opportunities for Foreign 

 Students at Colleges and Universities In the United 

 States." Students of education will find in it an excel- 

 lent account of the present facilities for higher educa- 

 tion in the States. Every kind of information that an 

 intending student can require is provided. Prominence 

 is given to descriptions of the organisation of a typical 

 American university, living conditions, college life, and 

 college entrance requirements. With reference to the 

 expenses of foreign students, Mr. Capen points out that 

 these vary widely at different institutions. Practically 

 all the privately endowed institutions charge annual 

 tuition fees. The fee is rarely less than 8/. a year for 

 collegiate instruction, and In some cases Is as high, as 

 30Z. or 40Z. a year. Professional Instruction, particularly 

 in medicine and engineering, is still more expensive. 

 The Massachusetts Institute of Technology charges 

 50Z. a year, and to its students In naval construction 

 and naval architecture looi!. a year. Most State-aided 

 institutions charge only a small tuition fee to collegiate 

 students not resident in the State, State residents 

 being generally given free instruction. Living ex- 

 penses, aside from tuition and other fees, vary with the 

 location of the Institution. As a rule, the fundamental 

 charges — room, board, and laundry — are rather lower 

 at country institutions than at those in the cities. 

 The possible wide variations in price are indicated by 

 the figure i8s. quoted as the weekly minimum by the 

 University of Minnesota, and 2I. Ss. the weekly maxi- 

 mum mentioned by Cornell University. The Incidental 

 expenses of city living, Including amusements, should, 

 of course, also be reckoned. 



On December 9 Mr. Patrick Alexander, well known 

 b}' his pioneer work in aeronautics, made over 

 to the headmaster of the Imperial Service College,. 

 Windsor (Mr. E. G. A. Beckwith), the munificent sum 

 of io,oooZ. " for the furtherance of the education of 

 boys of the Imperial Service College, i.e. for the train- 

 ing of character and the development of knowledge."' 

 Mr. Alexander had given to the college an aero- 

 laboratory and equipment about five years ago, but 

 owing to long absences abroad, and a serious illness, 

 he has been unable to Identify himself with the college 

 of late as heretofore. Having, however, taken up his 

 residence In Windsor for the last six months, he has 

 been able to continue his research work In the labora- 



