PLANTS WHICH PRODUCE WOOD 3 



durability, are more entensively used tlian any other class of 

 woods. The Maidenhair-tree of China and Japan [Ginkgo hiloba) 

 is exceptional among conifers in having broad leaves : neither this 

 tree nor the Yew can be said to bear cones, though their seeds are 

 naked : the Yew is destitute of resin ; and the epithet " soft- 

 wooded " applies to Willow, Poplar, Horse-chestnut, etc., as truly 

 as to conifers. 



The second and higher division of seed-bearing plants, the 

 Angiospermse, is divided into two Classes, which, whilst agreeing 

 in having their seeds enclosed in fruits, differ in many characters, 

 and in none more than in the structure of their stems. They are 

 known botanically, from the number of seed-leaves or cotyledons 

 of their embryos, as Monocotyledons and Dicotyledons. The Mono- 

 cotyledons, with one such seed-leaf, comprise hlies, orchids, 

 bananas, palms, sedges, grasses, etc. Pew of these, such as 

 Palms and Bamboos, reach the dimensions of trees, and those 

 which do so have generally unbranched stems which do not as 

 a rule increase in diameter after the very earliest stages of their 

 growth, the wood in them being confibaed to isolated strands 

 crowded together towards their outer surfaces. Though such 

 stems may occasionally, like those of tree-ferns, be utihzed " in 

 the round," and veneers, cut from the outer part of the stem 

 of the Cocoa-nut Palm [Cocos nucifera), and known, from the 

 appearance of the dark-coloured woody strands in the lighter 

 ground- tissue, as " Porcupine-wood," are used for inlaying. 

 Monocotyledons may well be ignored as economic sources of 

 wood. 



Dicotyledons, so named from having two seed-leaves to the 

 embryo, comprise an immense and varied assemblage of plants, 

 a very large proportion of which are merely herbaceous, never 

 forming wood. In those perennial members of the Class, how- 

 ever, which acquire the dimensions of trees or shrubs, the stem 

 generally branches freely, has a separable " bark," and increases 

 in girth with age ; the wood, though, as we shall see, it differs 

 in several important but not very obvious characters, agreeing 

 with that of conifers in being arranged in rings produced in 

 successive seasons (Fig. 1). 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, is in consequence 

 correctly termed exogenous, from the Greek ex, outside of, and 

 genTiao, to produce. The term endogenous, stiU sometimes applied 

 to the structure of the stem of monocotyledons, is less accurate. 



X"~" ""JU 



