FORM AND POSITION OF THE TRANSPIRING LEAVES AND BRANCHES. 



337 



peculiarity In the Spanish flora, for example, is an Umbellifer (Buplturum 

 vemcale) whose leaves are so twisted with regard to the sun that they remind one 

 forcibly _o the Australian acacias. Many Composites, especially the widely-distri- 

 buted Wild Lettuce (Lactuca Scariola), growing on dry soil in Central Europe 



Fig. 84. Compass Plants. 



1 Silphium laciniatum, seen from the east. * The same plant seen from the south. * Lactuca Scariola, seen from the east. 

 * The same plant from the south. Both species are considerably reduced. 



exhibit this contrivance in a striking manner. A Composite shrub, Silphium 

 ladniatum, to be found in the prairies of North America, from Michigan and 

 Wisconsin as far south as Alabama and Texas, has obtained a certain renown by 

 reason of the remarkable twisting of its leaf -blades. It long astonished hunters 

 in the prairies that in these plants (represented in fig. 84) the leaf -laminae, especially 

 those springing from the lowest portions of the stem, not only assumed a vertical 



VOL. I. 22 



