&4^ ^'H^perhnents arid Oljlr'Vatians 



tremity of their principal root, wliile in the other papts they' 

 vcre found and vigorous, fome oi the plants even role to the 

 funnnitof the bottle: in a word, I did not fee any difterence 

 between thefe plants and thofe whieh vegetate naturally in 

 the earth, except that thofe in the dark bottle had the jiem and 

 fmall roots longer and whiter, and the cotyledons greener. 



From thefe obfervationslhcre is reafon to conclude, that 

 if philofopl^crs have been long acquainted with the influence 

 of light on vegetation, they knew but iniperfe6lly * that the 

 fird degree of vegetation, that is to fay, the expanfion of the 

 germs of plants, requires obfcurity like that of the germs of 

 animals, fince light is evidently prejudicial to them 



If we rccolleft that the feeds of vegetables are all covered 

 with a pretty hard opake bark, we (hall be inclined to be 

 licve that this bark is not only deftined to defend them from 

 the prejudicial influence of the air, gafes, 8cc. but alfo to 

 ihelter the tender and fenfiblc germ from the action of the 

 folar light, which wo'.ild make tliem perifh. 



I fliall terriiinate this memoir with a remark which has 

 occurred to me in regard to the lite of embryos. In my 

 opinion, the vital power of embryos is expanded in a manner 

 very fmiple and common to all germs, and the only obje6t 

 of it is the expanlion of thofe organs, the exercife of which 

 is to form afterwards real life. Though thefe organs all exill 

 in the embryo, they have fcarcely any influence on the actual 

 hfe. The fafts which induce me to entertain this opinion 

 are, that the feeds of vegetables, deftitute not only of eyes 

 but even of a nervous fyitem, are ncverthelefs aliected by 

 hght as well as the germs of animals. 



Obfervatious made on the refpi ration of the eggs of ani- 

 mals h'^.ve (liow'n me alfo that thefe €ggs, during their, ex- 

 panfion, abforb oxygen gas; if this gas is not fupplied to 

 them, their expanfion is fufpended j and this- refpiration or 

 rather abforption of air may be accekratcd or fa fpcnded 

 i)V accelerating or checking the influence of the oxvgen, 

 >vhich has an influence on tlie expanlion of the jvenn. 



We are taught by the experiments of Mr. Cruickfliank 



* l\vo able pUiioloi hers, Senebitr, an«l my eouniryir.an Vaiiiilli, hz\e 

 maUtt.ih* Uimc pbftrvii'.on. 



that 



