Feb. 24, liSo/J 



NA TURE 



397 



strong argument for a silicon-cellulose in which silicon 

 might or might not with equal physiological convenience 

 play the part of one or more atoms of carbon. Fascinat- 

 ing as this hypothesis is, 1 am bound to say that the 

 prolonged investigation which he devoted to the question 

 is on the whole adverse to the idea of silicon playmg any 

 part of the kind. 



It still remains then an unsolved problem why, when no 

 adaptive end is involved, plants should take up such rela- 

 tively enormous quantities of silica. The case of the frus- 

 tules ol Dialoniacae is peculiar, as there the silicious wall is 

 apparently a continuous plate of inorganic matter capable 

 of resisting without impairment treatment by the most 

 destructive and disintegrating agencies known Yet 

 Castracane adduces evidence to show that such walls can 

 grow ; and as this can only be by interstitial growth, a 

 molecular constitution is implied quite different from any- 

 thing physical, and precisely similar to that of a cellulose 

 membrane. He quotes, indeed, von Mohl for the opinion 

 that the wall is not simply inorganic, " but only an organic 

 membrane which is impregnated with silex." 



Now, in the case of tabasheer, it is quite evident that 

 the plant takes up an amount of silica beyond its powers 

 to use, and so it is exuded into the hollow cavities of the 

 bamboo stem. I do not mind confessing that, in so far as 

 1 had reflected on the matter at all, I had pictured to 

 myself this as taking place by some process of secretion, 

 so that the mass of tabasheer ultimately accumulated from 

 successive portions of thrown-off silica. I was obliged, 

 however, to give a little more serious thought to the matter 

 when Prof. Cohn, of IJreslau, wrote to me that he proposed 

 to investigate the whole subject, and asked for help in the 

 way of specimens and information. It then struck me 

 what a very singular thing the phenomenon of the occur- 

 rence of tabasheer really was. 1 set to work to hunt up 

 in the literature of Indian botany some rational account of 

 the matter. The only ray of light I got was from the 

 " Forest Flora of North-West and Central India," by Dr. 

 Brandis, late Inspector-General of Forests to the Govern- 

 ment of India. Everyone who knows Dr. Brandis knows 

 that he gave to administration the energy he would more 

 willingly have devoted to scientific pursuits. I was not at 

 all surprised to lind, therefore, modestly hidden in his 

 book (p. 566) the key to the riddle. He says : It is not 

 at all impossible that the well-known silicious deposit 

 {tabasheer) which is found in the joints of this and other 

 species \Bambusii iiniiuii/iacea'\ may be the residuum of 

 the fluid which often fills the joints.' I communicated 

 this to Prof. Cohn, and he was good enough to tell me that 

 he quite agreed that this was the correct explanation. I at 

 the same time wrote to Dr. King, the distinguished Super- 

 intendent of the Royal Botanic Garden, Calcutta, to know 

 if it were possible to procure specimens of tabasheer /;/ situ, 

 as we possessed in our Museum nothing but broken frag- 

 ments. I extract from several letters he has written me 

 the following particulars : — "January 11. I have inquired 

 of several old workers as to the situation tabasheer occu- 

 pies. They all say it is found either on the Jloor of the 

 joint, or if (as is so often the case in B. Tuldd) the stem 

 leans over, it is also found on the lower wall. It is never 

 found on the roof of a joint. . . , . Tabasheer is not 

 common in bamboo grown near Calcutta. And, besides, 

 it is apt to be forced out of its natural position by the 

 forced used in breaking a joint open. There is no 

 external mark by which a tabasheer-bearing joint can be 

 recognised prior to being opened." "January iS. I have 

 got a specimen of tabasheer ;'« situ for you. It concretes 

 as a jelly, and is now being carefully dried off." 



I think that these extracts (in which the italics are mine) 

 fully confirm the explanation as far as I know first put 

 out by Dr. Brandis. The rapidity of growth of a bamboo 

 shoot is well known to be enormous. The root-pressure 

 is probably equally great. The joints, at first solid, become 

 hollow by the rending apart of the internal tissues, and 



water containing silica in solution is poured out into the 

 cavities so formed. When the foliage is developed, trans- 

 piration is active : the water taken up from the ground 

 is rapidly got rid of; not merely is the root-pressure 

 compensated, but the water poured out into the joints is 

 re-absorbed. It is not easy to see why the silica should 

 not be always taken with it, as in the vast majority of cases 

 it no doubt is. But in the cases in which it is left behind 

 it has apparently simply undergone a process of dialysis. 

 The determining causes of the occasional deposit of 

 tabasheer are, 1 think, still obscure. But, as Prof Cohn 

 intends to investigate the subject, I think we may pretty 

 confidently look forward to an exhaustive explanation. 



It is a well-known fact that a largre proportion of the 

 ash-constituents of plants may have but little significance 

 in their nutrition. The chemical constitution of plants, as 

 far as their ash is concerned, to a large extent varies with 

 the nature of the soil in which they are grown. It is quite 

 certain that they will in consequence take up a vastly 

 larger proportion of certain constituents than they can 

 turn to any physiological account. Tabasheer is a striking 

 instance of one such case. The calcareous masses found 

 in the wood of many Indian trees mentioned in N.'^ture:, 

 vol. xxi. p. 376, affords another. 



W. T. Thiselton Dyer 



ON THE EARLIER TRIPOS OF THE 

 UNIVERSITY OF CAMBRIDGE 



I HAVE read with great interest the papers by Mr. 

 Glaisher in Nature of December 2, 18, and 30, 

 18S6 (pp. loi, 153, and 199), entitled " The Mathematical 

 Tripos. ' Through the period common to Mr. Glaisher's 

 notes and my recollections, I believe that we are strictly 

 in agreement. I am able, however, to supply some little 

 histories (I wish these had been more numerous and more 

 certain) relating to transactions several years earlier than 

 those known, personally, to Mr. Glaisher, and I am desirous 

 that their memory should not be totally lost. There are 

 now few persons, perhaps none, whose recollections of the 

 University of Cambridge and of Trinity College go so far 

 back as my own. 



I first advert to the official course of undergraduates' 

 life. 



Shortly after introduction to the College in the October 

 Term of 1819, I attended, with all other freshmen, in the 

 Senate House or in the College Hall (1 believe the latter) 

 to take the oaths of allegiance and supremacy. With 

 great ardour I renounced the "damnable doctrine" thatthe 

 Pope of Rome could absolve subjects from their allegiance, 

 with several similar declarations ; and I also disclaimed 

 all connection with other Universities and Colleges, and in 

 particular with Wolsey's College at Ipswich. I believe 

 (but have no certain knowledge) that these puerilities 

 terminated a few years afterwards. 



The undergraduates were arranged in " sides," divided 

 under the official tutors under whom they were entered in 

 the College Lists. There were then two " sides ' ; sub- 

 sequently there were three. The lectures on each side 

 were held in the College rooms of the tutor or his assistant 

 tutor. The lectures consisted, naturally, in proposals of 

 theorems and problems (in writing) and oral discussion of 

 the answers in a friendly style. 



The annual College examinations of the undergraduates 

 of all sides (collected), of each year of undergraduateship, 

 were held in the College Hall at the practical termination 

 of the May Term. The order of merit in each year, as 

 determined by these examinations, was published by lists 

 of names suspended in the College Hall. Small sums of 

 money, to be expended in honorary prizes, were assigned 

 to the First Class of each year. 



In the third year of undergraduateship arrived the time 



