PAKT I 



CHARACTERS OF THE GENUS 



THE COTYLEDON. Plate I, figs. 1-3. 



The upper half of the embryo in Pinus is a cylindrical fascicle of 4 to 15 cotyledons (fig. 1). The 

 cross-section of a cotyledon is, therefore, a triangle whose angles vary with the number composing 

 the fascicle. Sections from fascicles of 10 and of 5 cotyledons are shown in figs. 2 and 3. Apart from 

 this difference cotyledons are much alike. Their number varies and is indeterminate for all species, 

 while any given number is common to so many species that the character is of no value. 



THE PRIMARY LEAF. Plate I, figs. 4-6. 



Primary leaves follow the cotyledons immediately (fig. 4) and assume the usual functions of foliage 

 for a limited period, varying from one to three years, secondary fascicles appearing here and there 

 in their axils. With the permanent appearance of the secondary leaves the green primaries disappear 

 and their place is taken by bud-scales, which in the spring and summer persist as scarious bracts, 

 each subtending a fascicle of secondary leaves. At this stage the bracts present two important dis- 

 tinctions. 



1. The bract-base is non-decurrent, like the leaf -base of Abies fig. 5. 



2. The bract-base is decurrent, like the leaf -base of Picea fig. 6. 



The two sections of the genus, Haploxylon and Diploxylon, established by Koehne on the single 

 and double fibro-vascular bundle of the leaf, are even more accurately characterized by these two 

 forms of bract-insertion. The difiference between them, however, is most obvious on long branchlets 

 with wide intervals between the leaf-fascicles. 



The bracts of spring-shoots are the scarious bud-scales of the previous winter; but the bracts of 

 summer-shoots have the form and green color of the primary leaf. 



THE BUD. Plate L figs. 7-11. 



The winter-bud is an aggregate of minute buds, each concealed in the axil of a primary leaf con- 

 verted into a scarious, more or less fimbriate, bud-scale. Buds from which normal growth develops 

 appear only at the nodes of the branches. On uninodal branchlets they form an apical group consist- 

 ing of a terminal bud with a whorl of subterminal buds about its base. On multinodal branchlets 

 the inner nodes bear lateral buds which may be latent. 



Fig. 7 represents a magnified bud of P. resinosa, first immersed in alcohol to dissolve the resin, then 

 deprived of its scales. This bud contains both fascicle-buds, destined for secondary leaves, and larger 

 paler buds at its base. These last are incipient staminate flowers, sufficiently developed for recogni- 

 tion. Such flower-bearing buds are characteristic of the Hard Pines in distinction from the Soft 

 Pines whose staminate flowers cannot be identified in the bud. 



The want of complete data leaves the invariability of this distinction in question, but with all 

 species that I have examined, the flowers of Hard Pines are further advanced at the end of the sum- 

 mer. In the following year they open earlier than those of Soft Pines in the same locality. The stami- 

 nate flowers of some Hard Pines (resinosa, sylvestris, etc.,) are not apparent without removing the 

 bud-scales, but, with most Hard Pines, they form enlargements of the bud (fig. 9). 



