FOKM AND POSITION OF THE TRANSPIRING LEAVES AND BRANCHES. 



337 



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

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

 forcibly of 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. 



^Silphium laciniatum, seen from the east. 2 xhe same plant seen from the south. 3 Lactuca Scariola, seen from the east. 

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



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

 laciniatum, 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 



Voi. L 22 



