372 



SCIENCE- G OS SIP. 



Floating Foraminifera.— In reference to Dr. 

 G. H. Bryan's interesting article entitled " Experi- 

 ences in Floating Foraminifera " {ante, p 290), it 

 may be useful to tho->e who are working in the 

 same direction to know that calcareous and other 

 light mineral substances can be separated from 

 heavier in sands by making use of the blast of an 

 ordinary blowpipe. There is a note in the " Geo- 

 graphicalJournal," May 1897, on " Drifting Sands " 

 that fully explains my meaning. A little practice 

 soon enables the student to determine the strength 

 of blast necessary for the separation of particles 

 varying in size and density in any given sand-mass. 

 The sand should be allowed to fall through a small 

 paper funnel, and the descending stream " played " 

 upon with a constant blast of uniform pressure. 

 The method I employed for separating sand con- 

 stituents by means of a vibrating inclined plane 

 {vide " Nature," vol. xxxix. 1889, p. 591) is useful 

 when it is desired to collect samples of the denser 

 minerals only. The inclined plane of " frosted " 

 glass which I made use of in my researches on 

 " musical " sands (see " Musical Sand," 1888) is 

 the best method that can be adopted for bringing 

 about the separation of rounded grains from those 

 of the angular type. I shall be pleased to send 

 any of your readers who are interested in the study 

 of sands a copy of my note on "Drifting Sands. — 

 Cecil Cams- Wilson, Royal Societies Club. S.W., 

 March 1th, 1901. 



ANSWERS TO CORRESPONDENTS 



G. B. (Darlington). — I am obliged to you for 

 your letter, and am glad that the article referred 

 to interested your Society. The specimen you 

 send is, as you suggest, a dendrite on limestone. 

 Such dendrites are frequently met with, and you 

 will find them illustrated in text-books on geology. 

 They are due to thin films of mineral matter that 

 have formed between fissures or joints in the rock, 

 and in so doing have branched out into this moss- 

 or fern-like appearance. The fissure is necessarily 

 a very fine one — so fine as to be almost invisible 

 without the aid of a pocket lens. You will find an 

 interesting illustrated article on dendrites by Mr. 

 Carrington in Science-Gossip, vol. i., N.S., p. 267. 



G. E. H. (Hornsey). — I have never tried to 

 make permanent mounts of amoebae, and cannot 

 therefore speak from my own experience, but 

 I would suggest fixing with 2 per cent, chromic 

 acid added to the water containing the amoebae 

 in a watch-glass. This is one of the methods re- 

 commended by Lee. As dilute stains you might try 

 methyl-green, Bismarck brown, or haematoxylin, 

 and as mounting medium, glycerine or Farrant's 

 solution. I am sorry I cannot give you more 

 definite information. Will you let me know what 

 results you get, for the benefit of other micro- 

 scopists ? Minute Crustacea, such as Cyclops and 

 Daphida. are generally mounted unstained in 

 Canada balsam, after soaking in turpentine ; and 

 the same applies to Hydra. You can fix with 

 alcohol and so get rid of the water. Weak osmic 

 acid will both kill and often differentiate the 

 tissues ; but be very careful with this reagent, as its 

 vapour is most irritating to both eyes and throat. 

 Perhaps the best stain is picro-carmine. All the 

 above reagents etc. can be obtained from Chas. 

 Baker, or Watson & Sons, both of High Holborn, 

 W.C. I am afraid there is no other book dealing 

 with the mounting of the above, other than Lee's 



" Microtomist's Vade-mecum, 

 advanced methods only. 



which deals with 



MEETINGS OF MICROSCOPICAL SOCIETIES. 



Royal Microscopical Society, 20 Hanover Square, 



London. May 15, 8 p.m. 

 Quekett Microscopical Club, 20 Hanover Square, 



London. May 3, 17, 8 p.m. 



For further articles on Microscopic subjects see 

 pp. 353 and 358. 



EXTRACTS FROM POSTAL MICROSCOPICAL 

 SOCIETY'S NOTEBOOKS. 



[Beyond necessary editorial revision, these 

 extracts are printed as written by the various 

 members. Correspondence thereon will be wel- 

 comed. - Ed. Microscopy, S.-G.] 



Sections through Stems of Brazilian 

 Lianas. — The term Lianas was first used in the 

 French colonies and afterwards adopted by English, 

 German and other travellers to designate the 

 woody, climbing and twining plants which abound 

 in tropical forests and constitute a remarkable and 

 ever-varying feature of the scene. They over- 

 top the tallest trees, descend again to the ground 

 in vast festoons, pass from one tree to another, and 

 bind the whole together in a maze of living net- 

 work. Many lianas become tree-like in the thick- 

 ness of their stems, and often kill by constriction 

 the trees which originally supported them. 

 Botanically considered, lianas belong to orders 

 which are often quite different. — John Terry. 



The mounter of tfhese sections states that the 

 peculiar distribution of the wood is due to the 

 cohesion of other stems. I have looked in the 

 " Encyclopaedia Britannica " and other large works 

 of reference, but can find no information concern- 

 ing these plants. Travellers in tropical regions 

 refer to the wonderful growths of the forest, but 

 they rarely give any of those minute details which 

 are essential in such cases as the one before us. 

 Yet, though I do not know anything of these 

 plants, I have no hesitation in saying that I do not 

 believe this cohesion theory. Take, for instance, 

 fig. 1. The central portion starts on its journey 

 through life ; it comes across two companions, who 

 metaphorically link arms and agree to unite and 

 travel together. By-and-by they come across two 

 more, and they likewise agree to accompany them, 

 also one on each side ; soon they find two more, - 

 little ones this time, and persuade them to 

 join the company. Now, it will be noticed 

 that they always seem to join on in pairs, one 

 on each side, and that one side numerically 

 balances the other, whilst each woody area on 

 the right exhibits nearly the same development 

 as its counterpart on the left, even down to the two 

 little ones at the extremities ; further, that each 

 woody area exhibits the same structure as its 

 neighbour. Chance acquaintances do not usually 

 exhibit such a singleness of purpose and formation. 

 Secondly, what has become of the organic centres 

 or axes of these coherent members ? How, on this 

 theory, account for the unbroken sclerenchyma 

 (the hard bast) encircling the entire section, or 

 its absence in the interior, and where are the 

 remains of the cortices of the last arrivals ? To my 

 way of thinking, this theory gives no answer. In 

 the hot and humid atmosphere of these tropical 



