INTRODUCTION 3 



though the former epithet is equally applicahle to> 

 WiUow, Poplar, or Horse-chestnut, whilst the Yew is 

 destitute of resin, and does not bear cones. 



The Angiosperms, the higher division of seed- 

 bearing plants, are divided into two Classes, the 

 Monocotyledons and the Dicotyledons, which agree 

 in little except in having their seeds enclosed 

 in fruits. The Monocotyledons, named from the 

 seed producing but one primary leaf, or cotyledon, 

 comprise Lilies, Orchids, Palms, and Grasses, few of 

 which, and those only tropical forms, such as Palms, 

 reach the dimensions of trees. 



Dicotyledons, so named from having two seed- 

 leaves to the embryonic plant, comprise an immense 

 and varied assemblage of plants, most of which are 

 herbs, never, that is^ forming wood. In those perennial 

 members of the Class, however, which acquire the 

 dimensions of trees, the stem generally branches 

 freely, has a separable " bark," and increases in girth 

 with age; the wood, though it differs in several 

 important characters from that of Conifers, agreeing 

 with it in being arranged in annual rings. These 

 rings, as they appear in a cross-section of a tree, or 

 conically tapering sheaths surrounding the tree, as 

 they in fact are, form on the outside of the wood 

 of previous seasons and beneath the bark; and this 

 type of stem, characteristic of Gymnosperms and 

 Dicotyledons, i.e. of all our familiar trees, is in 

 consequence termed exogenous, from the Greek ex, 

 outside of, and genna'd, I produce. Dicotyledons are 

 commonly slower of growth than Conifers, and their 

 wood, especially that near the centre of the stem, 



