THE CLUSTER PINE 35 



projections of the corky layer of the bark kaown- 

 as " J)ulvini." Hard and rigid in texture, with a 

 single riiidrib and without any lateral veins, the 

 needle-shaped leaves are, as we have seen, specially 

 adapted to dry or "xerophytic" surroundings, and 

 the position of their resin-ducts and other internal' 

 structure serves as a means of discriminating the 

 species. 



One very important character for the classifica- 

 tion of the Abietince, however, is afforded by the 

 leaf- arrangement. Whilst in the Firs ' (Abies) ^ 

 DoiTglas Fir (Pseudotsu'ga), Hemlock Spruces 

 {Tsiiga), and Spruces (Picea), the trees only bear 

 one kind of shoot, those, namely, of unlimited 

 growth, and the leaves spring singly from these 

 shoots, Cedars, Larches, and Pines bear their leaves 

 in a more or less tufted manner, producing both 

 long and short, or dwarf shoots — shoots, that is, of 

 unlimited and of limited growth. In Larches and 

 Cedars, both kinds of shoot bear needle-like leaves. 

 The genus Pinus is widely different, its long 

 shoots bearing nothing but scale-leaves, while the 

 dwarf shoots have both scale-leaves and needles. 



The flowers of the Abietince are always monoe- 

 cious. The staminate or male flowers are col- 

 lected in dense clusters near the ends of the last 

 year's ghoots, each consisting of an elongated axis 

 bearing several membranous bracts at its base, and 

 a cylindrical mass of densely and spirally arranged 

 yellow stamens. Each stamen consists of two 

 pollen-sacs on a scale-like "sporophyll" or "fila- 

 ment," which expafids at the apex iiito a " eon- 



