DICOTYLEDONE^E. 71 



rarely ripens seed. Where a succession of young- 

 stems rising- from the roots of the old trees is con- 

 sidered desirable, grafted plants should not be 

 chosen; but those raised from layers only. Elm 

 timber is tough and durable, but very liable to warp, 

 owing- to its sap being* so slowly fugitive ; as it con- 

 tinues to shrink for twenty years after being used as 

 weather-boarding. 



In considering- the physiology and the vegetative 

 powers of the elm, we are struck with how little one 

 part of the system depends on the others. The 

 whole axis of wood may be scooped, or rotted out 

 even to the last year's alburnum, and still the outside 

 shell, consisting of little besides the vital envelope 

 and bark, will continue to put forth new shoots ; and 

 even if severed from the root and decapitated, the 

 butt, lying in a shady place, \^1 still expert shoots 

 and leaves for several years. 



The next order is the Urticece, and of this we 

 may venture to assert, that were the different genera 

 it contains assembled together so as to be seen at a 

 glance, no one but a rig-id systematic botanist would 

 pronounce it a natural association. Here we find the 

 cultivated fig, and the common nettle; the bread- fruit 

 tree and the hop ; no two of which bear the least 

 resemblance to each other. But, as all the genera 

 agree in their mode of florescence, they are, on this 

 account only, brought together. Notwithstanding 

 the dissimilarity among the plants forming- this order, 

 several of them have a property in common which 



