( 188 ) 



more pieces of platiiiinn gauze were fixed horizontally, on wliicli a 

 patch of muslin or cotton was placed. The trough \vas tilled with 

 Avater as high as the patch, in some experiments it contained oil or 

 only air; then the mercury was poured on the patch. The tension 

 of the lower mercnry-surface was great enongh to prevent the mercury 

 from being forced through the meshes. 



Now Payer made various seeds germinate in the layer of water 

 on the mercury. It will be presently seen that he fixed the seeds to 

 some extent. Of some he saw the roots penetrate through a layer of 

 mercury of as much as two centimetres and appear in the \vater 

 under it. Of other seeds the roots remained creeping on the mercury, 

 of others still they only penetrated a few millimetres. Hence Paykr 

 concludes that the roots have a different penetrative power, not 

 depending on differences of weight, stiffness or size. Weight alone 

 cannot be the cause, for if the roots are taken from the mercury 

 they do not sink in it again. They remain floating and oidy the 

 growing part can i)enetrate again. Difl'erences in stiffness cannot cause 

 the varying behaviour, any more than differences in size. For roots 

 of garden-cress (Lepidium sativum) do penetrate, those of buckwheat 

 do not, although the latter are bigger, stiffer and heavier than (he 

 former. 



Of the committee wliici» had to report on tiiis paper by Payer, 

 DuTROCHET (since 1831 an ordinary member of the Académie) was 

 the reporter. The report was late in appearing and meanwhile on 

 March 24,1845, Durand sent a pai)er to the Académie in which he 

 thought to be able to reconcile the conflicting opinions. 



Durand says in the extract of his "Mémoire sur un fait singulier 

 de la physiologie des racines" ') about the experiments of Pinot, 

 Mulder and Payer: "J'avais toujours vu la, an contraire, une de ces 

 experiences trop légèrement faites et illégitimement imposées a la science, 

 dont elles faussent on paralysent les inductions : un fait a rayer des 

 catalogues physiologiques." Therefore he wants to repeat these experi- 

 ments and to give their normal explanation. He makes a clear 

 distinction between loose and fixed seeds. He gives the following 

 synopsis of the cases which can occur. 



1. The seed is fixed above the mercury ; the root then penetrates 

 into the mercury perpendicularly to a depth of more than 4 

 centimetres. 



2. The seed is loose. Here we have two cases : 



.1. It reaches the margin of the mercury -surface. Then the root 



1) Gompies rendus Tome XX 1845 pag. 861—862. 



