1914] THOMSON—SPUR SHOOT 367 
they attain their mature condition. This is also true of the other 
fascicle-leaved conifers, sometimes only one or two needles develop- 
ing in the season that the spurs appear. There must thus be some 
common physiological reason underlying this feature, and no doubt 
it is the well known lack of vegetative vigor in the seedlings of the 
conifers generally. During the first few years they are busy estab- 
lishing a root system and there is little stem growth. Foresters 
and nurserymen know this early critical stage in the life of the 
conifers only too well. The growth in these early years could be 
measured in inches, while in later years it would require feet. 
I have examined older forms, 6-15 years old, of a large number 
of different species belonging to all the different sections of the 
pines, and have found supernumerary needles quite common, 
especially on vigorous specimens. On the main axis of one unusu- . 
ally sturdy plant of P. Strobus, a plant which had made at least a 
foot and a half of stem this year, and this stem fully three-quarters 
of an inch in thickness at its base, there was a spiral sequence of 
fascicles with 6, 7, 8, 9, and 10 needles. Fig. 4 is of one of these. 
The supernumerary needles have been surrounded by a rubber 
band, and it will be seen that they show a spiral gradation in length. 
This is a feature which to a less degree is sometimes shown by the 
5 original needles themselves. It is indicative of the concealed 
spiral arrangement of the leaves on the spur. This feature, I find, 
was observed long ago by MEEHAN (22), and its significance noted. 
The series of spurs referred to above occurred on the lower part 
of the year’s growth. It is more usual, however, to find spurs 
with extra needles near the apex of the season’s growth. I have 
found many instances of this in a mixed plantation of pines about 
8 years of age, which consisted of P. Sirobus, P. silvestris, and P. 
Banksiana, Of the white pine there was a large proportion of 
vigorous specimens with supernumerary needles. The Banksian 
pine showed few instances, but in the Scotch pines they were very 
numerous. I should think fully 75 per cent of these had several 
(3-6 or 7) trifoliar spurs at the apex of the year’s growth. These 
trifoliar spurs could be traced for two to three years previously 
at the corresponding places on the stem. The occurrence of tri- 
foliar spurs in this species at the branch region was observed by 
