1914] THOMSON—SPUR SHOOT 365 
on young vigorous trees and on fertile branches.” In P. Pinea, 
which usually has the leaves in pairs, ELwes and Henry (7, p. 
11g) state that ‘on well developed vigorous branches, a few of the 
leaves are sometimes in clusters of threes.” Of P. 7. orreyana, 
whose adult leaves are in fives, they also state (p. 106s) that “on 
young plants the leaves are frequently in clusters of 3 and 4.” 
Bortuwick (1) has described a tree of P. Laricio 12 years old with 
2, 3, and 4 leaves to the fascicle. The quadrifoliar spurs were 
found only at the top of the tree, which was of very vigorous growth. 
The variations in the number of leaves in the pines have been 
tecorded practically as isolated instances and have not been 
correlated. As they stand, they show that the spur shoot is not 
So definite and so specialized a structure as has been supposed, 
but that it is more in the nature of a branch with an indefinite 
number of foliage leaves. When, however, one looks farther into 
the variations from the standpoint of the spur being ancestrally 
a branch, it is evident that the fascicles with supernumerary needles 
should be found in the more primitive parts of the plant: on the 
seedling, on the fruiting branch, after wounding, etc. My own 
investigations have been along these lines, and though they do 
not completely correlate the cases reported, they go very far 
toward doing so and afford one important line of evidence of the 
branch character of the spur shoot. 
Fig. 1 is of the upper part of a 3-year-old seedling of P. Strobus.* 
Primordial leaves are unusually persistent on this plant, and may 
be seen among and below the three spurs with the rubber bands 
around their leaves. Brown scale leaves, however, replace these 
green seedling leaves around the base of each fascicle just as in the 
ordinary spur. The middle spur bears 15 leaves, the one to the 
Tight 11, and the one to the left 7. Fig. 2 is of a seedling of the 
Same species, one year older. The main axis in this case made a 
comparatively short growth the last season and bears 6 fascicles. 
The central one of these has g leaves, the one to its right 10, the 
two below these 7 each, the lowermost to the right 5 large and 2 
*I cannot determine absolutely that these and the other young forms are P. 
Strobus. It is possible that they are P. excelsa, but, since some consider the two 
sy as geographical varieties, the matter is unimportant from the present stand- 
t. 
