342 Miscellaneous. 



dimerous. The placentae, accordingly, are only two. The groove 

 on the stignia and the placentae are in line with the fertile stamens. 

 Here, therefore, is a symmetrical and complete, regular hut 

 dimerous orchideous flower, the first verticil of stamens not antheri- 

 ferous, the second antheriferous, the carpels alternate with these ; 

 and here we have clear (and perhaps the first direct) demonstration 

 that the orchideous type of flower has two stamineal verticils, as 

 Brown always insisted. — Silliman's Journal, September 1866. 



BoussingauW s Researches on the Action of Foliage. 



A full abstract of the first part of these investigations, communi- 

 cated to the French Academy of Sciences, is given in the ' Comptes 

 Rendus,' vol. Ix. no. 18 (May 1865). Theodore Saussure had long 

 ago ascertained that, while plants prosper and decompose carbonic 

 acid gas in an atmosphere containing as much as one-twelfth or even 

 one-eighth part of that gas, they promptly perish in unmixed car- 

 bonic acid, apparently without decomposing any of it, Boussingault 

 made his experiments in a better form, upon leaves only, avoiding all 

 complication of the action of the roots or other parts of the plant. 

 His results are : — 



1 . That leaves exposed to sunshine in pure carbonic acid do not 

 decompose this gas at all, or only with extreme slowness. 



2. But in a mixture with atmospheric air, they decompose carbonic 

 acid rapidly. The oxygen of the atmospheric air, however, appears 

 to play no part. 



3. Leaves decompose carbonic acid in sunshine as readily when 

 this gas is mixed with nitrogen or with hydrogen. 



Although this decomposition of carbonic acid by green foliage must 

 be a case of dissociation — a separation of carbon from oxygen — yet 

 Boussingault recognizes an analogy here with an opposite pheno- 

 menon, viz. with the slow combustion of phosphorus at the ordinary 

 temperature. Phosphorus in pure oxygen emits no light, does not 

 - sensibly undergo combustion, but does so in a mixture of oxygen with 

 atmospheric air, or with nitrogen, hydrogen, or carbonic acid. The 

 analogy may even be carried further ; for while a stick of phospho- 

 rus is not phosphorescent in pure oxygen at ordinary or increased 

 pressure, it becomes so in rarified oxygen. And Boussingault equally 

 ascertained that leaves which exerted no sensible action upon pure 

 carbonic acid at ordinary pressure, decomposed it, with the liberation 

 of oxygen gas, under diminished pressure. That is, rarefaction and 

 mixture with an inert gas act alike in mechanically separating the 

 atoms, whether of carbonic acid, as in the one case, or of oxygen, as 

 in the other, so as to determine the action either of combination or 

 of dissociation. 



In a continuation of these investigations (Comptes Rendus, vol. Ixi., 

 Sept. 25, 1865), Boussingault shows that carbonic oxide, whether 

 pure or diluted, is not decomposable by foliage, and that this inert- 

 ness of green foliage upon carbonic oxide goes to confirm the opinion 

 maintained in his ' Economie Rurale,' that leaves simultaneously de- 



