ROOT AND CROWN. 67 



Pelargoniums (as P. zonale, House-Geranium). In 

 most cases cauline leaves which lead the water 

 centripetally are either sessile or short-stalked, and 

 often clasp the stem with lobes or auricles. 



If the leaves are opposite and decussating, the 

 water is usually carried down in two channels, 

 which run along the stem from one pair of leaves 

 to the next. . . . 



When the leaves are not opposite, but are ar- 

 ranged in a spiral, the water filters down the spiral 

 from leaf to leaf. Many Thistles show this flowing 

 off of the water along a spiral line very beautifully. 

 With little grains of shot we may imitate the 

 action of the raindrops, and by this means see very 

 plainly, in plants with firm leaves, the path natu- 

 rally taken by the falling drops. Such grains of 

 shot dropped upon a growing plant of Alfredia 

 (Fig. II), 1 will roll down over the concave surface 

 of the upper leaf, and strike the stem which the 

 leaf clasps. Then, rolling over a lobe of the base 

 of the leaf, it will fall on the middle of the surface 

 of the leaf below, because the clasping auricles of 

 each leaf lie over the middle of the next lower 

 leaves. Thence the grains of shot fall on the third 

 leaf, and so on, till they reach the earth close to 



1 The Alfredia is a kind of thistle (Carduus cernuus). 



