GERMINATION. 14-1 



soft pulpy layer, usually of a white colour, which I 

 shall term the pulp- wood ! , sometimes inaccurately 

 named sap-wood. 



In succeeding years, besides this pulp- wood, we find 

 one or more rings of wood 2 , harder and closer in the 

 grain, the innermost being the hardest. This inner- 

 most ring forms what is termed the pith-tube 3 , which 

 is of various forms, being usually cylindrical, some- 

 times elliptical or angular, but always, according to 

 Du Petit Thouars, retaining the same dimensions at 

 every stage of growth. This tube encloses the pith 4 , 

 which is a light spongy substance, dry in old trees, but 

 moist in young trees, and in shoots and branches of 

 the first year, as may be seen in elder or bower tree. 



In herbs having two seed-lobes, the structure of the 

 stem is somewhat different, the distinction between 

 the two layers of bark, the pith-wood, the hard wood, 

 and the pith, being seldom apparent, though in endive 

 this is sufficiently distinct. In hemlock and cow- 

 parsnep, the centre of the pith forms a hollow tube 

 of considerable width. 



In the stem of grasses, corn, and reeds, instead of 

 pith, as in trees, the centre is hollow, and there are 

 only two parts whose structure is different. 



The stem of palms, though solid, more nearly re- 

 sembles that of the grasses than that of trees, though 



(1) In Latin, Alburnum ; in French, Aubier. 



(2) In Latin, Lignum. (3) In Latin, Tubus medullaris. 



(4) In Latin, Medulla, which is inaccurate. 



