146 INCLII^AtlON OF PLANTS TOVrARb8^I#EU<JHT. 



that the energy of this direction is greatest iathe most 

 herbaceous stalks, in whic/h the phenomeiion of etiolation 

 is also most remarkable. In forests the woody branches or 

 stems themselves may frequently be observed twisted to gaip. 

 an open place ; but this is because the unequal distribution 

 of light has continued several years ; the branches were 

 bent in their green state, and have acquired sohdity in that 

 in which they are found. Of this I have satisfied myself 

 by direct measures. Permit me here to observe, that it may 

 be possible to avail ourselves of this property of vegetables, 

 to formed curved timber for the purposes of the arts, by 

 dii'ecting the light on certain trees in a suitable manner. 

 The incUna- In the instances 1 have quoted it may be supposed, that, 



tion HI general Jf old branches do not bend, it is solely on account of their 



proportionate .-ii-. ■^ i , n-ti 



to the flexibi- hardness: and indeed it is evident, that, the more fiexible 



*'*y» the branch, the more will it be bent by the same quantity 



of partial etiolation; but a striking example will prove, 



but does not thai the inclination toward the light does not take place in 



take place m the most flexible branches, when they want the faculty of 

 plantH incapa- . . •' „ . , mi • 



ble ef deconi- decomposing carbonic acid gas by means of light. This ex- 

 posing car- ample is dodder. I have satisfied myself by direct experi- 

 as dodder.* ments, that it does not incline itself toward the light ; that, 

 placed under water in the sun, it does not decompose car- 

 bonic acid gas, and consequently can leng<iberi itself equally 

 on both sides, though unequally iHumined. 

 It depends The whole of the phenomenon then consists in tiie partial 



on a pa<-tial elonsration produced by etiolation. But it is known, that 

 elongation of , "^^ \ , ,-^ . • r. • i i i ■ i i 



the vessels, the elongation takes place chiefly in the vessels, which draw 



along with them as it were the cellular texture. Conse- 

 quently, the more vessels there are in a plant, or a part of 

 a plant, the more it ought to incline toward the light. In 

 ind is scarcely plants totally destitute of vessels, this inclination must be 

 IT'^t^f'^ d scarcely perceptible, because the rounded cells grow nearly 

 of spherical alike in all directions: hence this inclination toward the 

 '^'^■"'^- light is. next to nothing in .the cryptogamia, as in certain 



algjE composed Solely of rounded cellular texture. Those 

 of the cryptogamia, which, as the mosses for example, are 

 composed of two sorts of cellular texture, one with rounded 

 \- the other with tubular ciells, approdch the vascular plants 



»« cwisegj^uence of the lattery which i« capable of more or 

 tm :i less 



