66 EOOT AND CKOWN. 



mass of rootlets is embedded. In plants with root- 

 stocks, if the leaves are in a rosette and the rosette 

 lies on the ground, as with the Dandelion, Plantain, 

 etc., a channel or several main channels are to be 

 found on the upper side of the leaf, and the leaves 

 are always so arranged that the rainwater, falling 

 on the rosette, must flow towards the centre, from 

 which the root runs perpendicularly downwards. 

 If plants which guide the rainwater centripetally 

 have petioled leaves, they have also a distinct chan- 

 nel on the upper side of the leaf-stalk, which is 

 often deepened by the growth of a green border, 

 or sometimes a dry border, on both edges. The 

 channels on the stems of the radical leaves of 

 Rhubarb (Fig. 10), Beet, Peony, and most Violets 

 are especially interesting. 



The arrangements of plants with caul in e leaves 

 for carrying off the water are much more compli- 

 cated. When leaves on a stem high above the 

 ground catch rainwater, as the Rhubarb does, they 

 can keep their position better if their bases are 

 joined directly to the stem, or clasp it. If such 

 leaves were placed on long, upright stalks, they 

 would require an immense bulwark of supporting 

 cells, and, therefore, they are rarely petioled. 

 Among well-known plants we can only name some 



