November, 1912. 



KNOWLEDGE. 



SEXUALITY IN YEASTS.— As previously noted in these 

 columns ("Knowledge,'' 1911, page 106), the Yeast-fungi 

 iSaccharomycetesI have probably been derived from certain 

 simple sac-fungi (Asconiycetes) which have a definite vegeta- 

 tive plant-body or mycelium consisting of filaments and in 

 which a process of fertilisation occurs prior to the formation 

 of the spore-fruit. Since the publication of the note referred 

 to, several interesting new observations have been made which 

 appear to indicate the existence of a regression series in the 

 Yeasts, beginning with forms in which sexuality is pronounced 

 and ending with completely sexual forms. These observa- 

 tions are dealt with in papers by Guillermond iCotnptes 

 Rctuliis Soc. Biol., Paris, 1911) and by Nadson and 

 Konokotine {Bull. Jard. Imp. Bot., St. Petersburg, 1911). 



In the genera Schizosaccharomyccs and Zygosaccharo- 

 myccs the conjugating cells are alike, and the spores pro- 

 duced after conjugation vary in number from two to eight. 

 In S. octosporits, where eight spores (the typical number for 

 .AscomycetesI are formed, the two conjugating cells fuse com- 

 pletely into an ovoid cell, but in other conjugating Yeasts belong- 

 ing to these two genera the spores are fewer, and may either 

 be all formed in one of the two copulating cells (which after 

 union resemble two retorts with fused necks) or some in one 

 cell and the rest in the other. In Debaryomyces glohosus 

 the spore-producing cell (ascus) may either arise by copulation 

 as in Zygosaccliaroinyces, or without copulation, or by 

 conjugation of the mother-cell with a rudimentary bud which 

 it has previously given out and which becomes emptied back 

 into the mother-cell. In Schu-aniiioinyces occidentalis 

 there is no copulation, but the ascus shows an outgrowth 

 representing a conjugating tube which is functionless. In 

 W'illia anoiiiala the ascus is formed at the expense of an 

 adult cell which has absorbed the contents of a bud, sm.aller 

 than the mother-cell, the latter apparently functioning as a 

 male cell — this is sunilar to the third mode of ascus-forma- 

 tion just mentioned as sometimes occurring in Debaryomyces. 

 In Saccharoiiiycodes Liidwigii and W'illia Satiiniiis 

 conjugation does not take place: but during the formation and 

 maturation of the spores within the mother-cell nuclear 

 fu.sions occur, which according to Guillermond represent a 

 delayed sexual process. 



Nadson and Konokotine describe a new genus of Yeasts, 

 Guillermondia liavescens, in which conjugation occurs 

 between a smaller and a larger cell, the former having been 

 produced as a bud by the latter, which then produces an 

 ascus as an outgrowth ; into this the contents of the 

 ■■ fertilised " cell pass, and a single spore is formed, or in 

 some cases two spores. 



Though the interpretation of some of these fusions is 

 perhaps an open qi:estion, and it is doubtful whether the 

 phenomena described can in all cases be regarded as sexual 

 processes, these recent observations certainly strengthen the 

 links between the Yeasts and the lower typical Ascomycetes, 

 such as Eremascns and Endomyces. and they also appear 

 to indicate that in the Yeasts, as in the Saprolegniaceae, we 

 have a series of forms showing gradual loss of sexuality. 



CHEMISTRY. 



By C. .\ixswoRTH Mitchell, B.A. (Oxon.), F.I.C. 



A TOXIMETER FOR CARBON MONOXIDE. — .-^n 

 ingenious apparatus for detecting the presence of poisonous 

 proportions of carbon monoxide in the atmosphere is described 

 by M. A. Guasco in the Comptes Rendiis (1912. CLV, 282). 

 It is based upon the fact that when spongy platinum, or 

 platinum black, absorbs carbon monoxide there is a decided 

 increase of temperature. This is made apparent by means of 

 a differential thermometer in the form of a U tube, charged to 

 a certain height with a coloured liquid, .\bove this tube, and 

 communicating with it. are ,tw^o bulbs, protected from contact 

 with the atmosphere by a surrounding vessel, but provided 

 with porous membranes through which the gas can pass 

 by endosmosis. One of these bulbs is coated with the platinum 

 black, and any alterations in the temperature produced by the 

 absorption of carbon monoxide are immediately indicated by a 

 change in the level of the liquid in the U tube. The presence 



of as Httle as one part in ten thousand of carbon monoxide 

 may thus be detected, and by the addition of a graduated 

 scale the proportion of that gas may be estimated. Or, by 

 substituting mercury for the coloured litiuid in the tube, the 

 apparatus may be so arranged that, when a poisonous quantity 

 of carbon monoxide is reached, the expansion of the mercury 

 completes an electric circuit and rings a bell. 



USE OF PEAT FOR POWER PURPOSES. -A descrip- 

 tion is given by Mr. H. V. Pegg in the Journal of Gas 

 Lighting (1912, CXIX, 395) of the results of using peat in a 

 gas producer at Portadown. No preliminary drying of the 

 peat was required, although the moisture varied from about 

 eighteen to seventy per cent, according to the state of the 

 weather. The gas produced was of good ciuality, but excessive 

 spraying with water was necessary to remove the tar. while 

 the plant required cleaning about once a week. The tar 

 appears to be somewhat of a waste product owing to its 

 persistent pyroligneous odour, which has resisted all attempts 

 to remove. 



The use of peat instead of coal reduced the bill for fuel by 

 more than fifty per cent. The gas obtained from a peat 

 containing 44-6 per cent, of carbon, 5-42 per cent, of hydrogen 

 and 18-98 per cent, of moisture showed a calorific value of 

 144-0 B. Th. U., and had the following composition : — Carbon 

 dioxide, 10-6; carbon monoxide, 21-0; hydrogen, 13-0; 

 methane, 3-7; and total combustible matter, 37-7 per cent. 



VARIATIONS OF NICOTINE IN THE TOBACCO 

 PL.A.NT. — The increasing use of tobacco extracts as insecti- 

 cides has led to the cultivation of tobacco solely for this 

 purpose. Since the insecticidal value of the preparations 

 depends upon the proportion of nicotine they contain, they are 

 usuallv bought and sold on the basis of the amount of that 

 alkaloid present. 1 1 has, therefore, become a matter of practical 

 importance to ascertain at what period of its growth the 

 tobacco plant is richest m nicotine. In the experiments made 

 by MM. Chuard and Mellet iComptes Rcndiis, 1912, CLV, 

 293), with this object in view, it was found that there was a 

 material loss of the alkaloid when the fresh plant was dried. 



For estimating the proportions of nicotine in the growing 

 plant, seeds were sown on .April 25th, and analyses were made 

 of different parts of the young plants at irregular intervals. 

 On May 15th no nicotine could be detected, but a month later 

 (June 16th) the leaves contained 0-35 per cent., and the roots 

 0-15 per cent. By August 9th the nicotine in the leaves had 

 increased to 3-12 per cent., and in the roots to 0-69, while on 

 September ISth, the date on which the leaves were gathered, 

 the corresponding amounts were 4-79 per cent, in the leaves 

 and 0-64 per cent, in the roots. The stalks contained about 

 the same proportion of nicotine as the roots, while the amounts 

 in the shoots varied from 0-49 to over one per cent. 



Hence, the ordinary method of collection, in which only the 

 leaves are selected, involves a considerable loss of nicotine, 

 and it is suggested that a means might be devised for extract- 

 ing the alkaloid from the waste portions of the plant, and to 

 utilise the final residues for manure. 



NATURAL GASES RICH IN HELIUM.— The gases 

 emitted by some of the French mineral springs are particularly 

 rich in helium, as is shown by the following analyses published 

 by MM. Moureu and Lepape {Comptes Rendiis, 1912, CLV. 

 197) :— 



