74 COTYLEDONS. 



on an axis, by which their position was a little altered 

 every day. After the basket had thus made two or 

 three circumvolutions, the young roots were found to 

 have formed as many turns in attempting to attain their 

 natural perpendicular direction. Mr. Knight has ascer- 

 tained, Phil. Trans, for 1806, that a strong centri- 

 fugal force applied to vegetating seeds will considerably 

 divert the root from this direction outwards, while the 

 stem seems to have a centripetal inclination. 



The young root, if it grew in a soil which afforded 

 no inequality of resistance, would probably in every 

 case be perfectly straight, like the radical fibres of 

 bulbous roots in water ; but as scarcely any soil is so 

 perfectly homogeneous, the root acquires an uneven 

 or zigzag figure. It is elongated chiefly at its extre- 

 mity *, and has always; at that part especially, more 

 or less of a conical or tapering figure. 



When the young root has made some progress, the 

 two lobes, commonly of a hemispherical figure, which 

 compose the chief bulk of the seed, swell and expand, 

 and are raised out of the ground by the ascending 

 stem. These are called the Cotyledons, J\ 4. Be- 

 tween them is seated the Embryo or germ of the 

 plant, called by Linnaeus Corculum or little heart, in 

 allusion to the heart of the walnut. Mr. Knight deno- 

 minates it the germen, but that term is appropriated 

 to a very different part, the rudiment of the fruit. The 



* As may be seen by marking the fibres of Hyacinth roots in water, 

 or the roots of Peas made to vegetate in wet cotton wool. 



