THE LEAF. 41 



But temporary, still more definitely in the day, than in the 

 year. When you go out, delighted, into the dew of the morn- 

 ing, have you ever considered why it is so rich upon the grass ; 

 why it is not upon the trees ? It is partly on the trees, but 

 yet your memory of it will be always chiefly of its gleam upon 

 the lawn. On many trees you will find there is none at all. 

 I cannot follow out here the many inquiries connected with 

 this subject, but, broadly, remember the branched trees are 

 fed chiefly by rain, the unbranched ones by dew, visible or 

 invisible ; that is to say, at all events by moisture which they 



FIG. 3. 



can gather for themselves out of the air ; or else by streams 

 and springs. Hence the division of the verse of the song of 

 Moses : "My doctrine shall drop as the rain ; my speech shall 

 distil as the dew : as the small rain upon the tender herb, and 

 as the showers upon the grass." 



23. Next, examining the direction of the veins in the leaf of 

 the alisma, b, Fig. 3, you see they all open widely, as soon as 

 they can, towards the thick part of the leaf ; and then taper, 

 apparently with reluctance, pushing each other outwards, to 

 the point. If the leaf were a lake of the same shape, and its 

 stem the entering river, the lines of the currents passing through 



