Oct. 28, 1880] 



NATURE 



603 



the contents of the young sieve-tubes. Isolated drops or 

 irregular masses appear in the layer of protoplasm lining 

 the cell cavity before the disappearance of the nucleus. 

 These consist of a slimy %\.Vi^{Schl€im') apparently rich in 

 nitrogen.' The separate masses later fuse together to 

 form a band, which is usually much narrower than the 

 girth of the cell. Between this and the wall of the sieve 

 tube a protoplasmic envelope intervenes {Hiilhclilaucli). 

 The central cavity within these is filled with " sieve-tube 

 sap." For further details concerning the contents of the 

 sieve-tubes the reader must be referred to the original 

 work. 



The author has not been able to observe directly the 

 first appearance of connection through the pores of the 

 sieve ; but suggests that it is effected by the outgrowth of 

 protuberances of the envelope {Hiillschlauch) from oppo- 

 site sides of the sieve, which penetrate it and coalesce to 

 form the connecting strings. 



The presence of starch grains noticed by Briosi is con- 

 firmed by Wilhelm in Vitis. He finds them in members 

 of sieve-tubes which are still closed. He opposes the 

 idea that they pass through the sieve on ground of their 

 size. In Cucurbita and Lagenaria they are absent. Be- 

 sides the communication of sieve-tubes with one another 

 laterally, so as to form a complete system, Dr. Wilhelm 

 has observed in the case of Vitis a further connection, 

 through the medullary rays, of tubes lying on opposite 

 sides of the ray. This is effected by special sieve tubes, 

 produced by transformation of cells of the medullary ray, 

 so as to form a series of very short members ; these 

 correspond in development and structure with the ordinary 

 sieve-tube. They traverse the medullary rays in an 

 obliquely tangential direction. Such communications are 

 not found in Cucurbita or Lagenaria. 



The question of function has not been solved by these 

 observations. Dr. Wilhelm still holds the view, pro- 

 pounded by Niigeli, that the function of the sieve-tube 

 is the transference of indiffusible substances from place 

 to place in the plant. 



In conclusion it maybe remarked that the paper is well 

 written, but that it is of such a character as to be interest- 

 ing only to the specialist. The plates, of which there are 

 nine, are executed with great skill and exactitude. 



F. Orpen Bower 



OUR BOOK SHELF 

 The Elementary Geometry of Conks. By C. Taylor, 

 M.A. Third Edition. (Cambridge : Deighton, 1880.) 

 Mr. Taylor has been before the public as a writer on 

 geometrical conies since 1863, in which year he brought 

 out his " Geometrical Conies " ; in 1872 we have the first 

 edition, and in 1873 t^e second edition of his "The Geo- 

 metry of Conies," a smaller work than his first book (1863). 

 Now we have a third edition with the above title. In 

 May, 187s, Mr. Taylor, in a paper entitled "On the 

 Method of Reversion applied to the TransfoiTnation of 

 Angles" (read before the Iklathematical Society, and 

 subsequently printed in a more extended form in the 

 Quarterly Journal, No. 53, 1S75, ^'th the title "The 

 nomographic Transformation of Angles"), called atten- 

 tion to a '■ neglected work on conies by G. Walker, 

 F.R.S. (1794)": in tliis work we first meet with the 

 properties of a circle, which Walker calls the generating 

 circle, but which Mr. Taylor, in the work before us, styles 



' Cf. De Bary, " Vergl. Annt.," p. 185. 



the eccentric circle ; in the free use of this circle consists 

 the main feature in the alterations made in this new edi- 

 tion ; further, though still keeping well in view the proving 

 chord-properties independently of tangent-properties, there 

 is a rearrangement of the text ; so that the two properties 

 are not treated of in distinct chapters. In other ways 

 also we think this little work is improved, but we need 

 say no more upon a third edition. 



LETTERS TO THE EDITOR 



[The Editor does not hold himself responsible for opinions expressed 

 by his correspondents. Neither can he undertake to return, or 

 to correspond with the writers of, rejected manuscripts. No 

 notice is taken of anonymous communications.'\ 



[ The Editor urgently requests correspondents to keep their letters as 

 short as possible. The pressure on iiis space is so great that it 

 is impossible otherwise to ensure the appearance even of com- 

 munications containing interesting and no^el facts.'\ 



Ceraski's New Variable Star 



Unless the principal fact mentioned below has already come 

 to your notice, you may like to bring it before the astronomical 

 public in the columns of Nature. 



The true period of the variable star recently discovered at 

 Moscow {Durchmusterung, zone -(- Si°, No. 25) appears to be 

 two days and a half, instead of five as given in Nature, vol. 

 xxii. p. 455. Minima were observed at the Harvard College 

 Observatory on September 23 ar.d 28. The claanges of the star 

 will accordingly be visible in England on October 13, 18, 23, 

 28, &c., during the three or four hours before or after midnight. 

 The rapidity of the change is probably greater in the case of 

 this star than in that of any other known variable, the variation 

 exceeding a magnitude in the course of one hour. The total 

 variation is more than two magnitudes. A star of about the 

 eighth magnitude (No. 30 of the same zone) is within a few 

 minutes of the variable, and may readily be compared with it. 

 The phenomenon of the variation is consequently a striking one, 

 even as seen in a small telescope. The approximate place of 

 the variable for 1881 is inR.A. oh. 51m. 4SS., Deck -1-Si° I4''l. 

 Edmund C. Pickering 



Harvard College Observatory, Cambridge, U.S., October 2 



S Lord Lindsay's Dun Echt Circular, No. 10, which I received 

 on Saturday morning, October 23, prepared me to watch for a 

 probable minimum of M. Ceraski's remarkalde variable star 

 B.D. -h 81° 25' on the same night. From my observations the 

 minimum appears to have occurred at about iih. lom. G.M.T., 

 the Star then being of about g'l magnitude. At gh. 5m. I noted 

 it about equal to a neighbouring star, B.D. -J- Si' 30', which I 

 gauged S'l mag., and at I3h. 50m. it bad regained the same 

 magnitude. When about minimum I thought the variable to be 

 slightly ruddy, but as it brightened up again it lost this tint and 

 appeared to be white, or bluish white, as when I first observed 

 it. It has a small bluish 11 i mag. companion, the P. and D. of 

 which I roughly estimated to be 60° and 10" respectively. The 

 star was observed by Carrington in 1S55, on December 19, 21, 

 and 30, his estimated mags, being S'O, S'o, g'o. Possibly the 

 star may have been near minimum at his third epoch. 



Knowles Lodge, Cuckfield, October 25 George Knott 



" Solid Ice at High Temperatures " 

 The interesting results announced by Prof. Thomas Caruelley, 

 of Firth College, Sheffield, in relation to the physical conditions 

 under which ice persistently maintains its solid state when 

 exposed to the influence of heat (N.\TURE, vol. xxii. p. '435), 

 deserves some notice. When he speaks of obtaining "solid ice 

 at temperatures so high that it was impossible to touch it without 

 burning one's self," it is evident that this burning quality apper- 

 tains to the hot vessel containing the ice, and not to the solid ice 

 itself. For it is obvious that under the given conditions the 

 temperature of the surface of tlie ice is kept at least as low as 0° C. 

 ly the rapid vaporisation of it while in a solid state. 



The phenomenon of a body remaining persistently at a low 

 temperature when surrounded by a hot vessel — through the 

 influence of the rapid change of state — is analogous to the 

 well-known re-ults of Boutigny and Faraday in relation to the 

 freezing of water and mercury in a hot vessel by means of lavge 



