444 BOTANICAL GAZETTE [NOVEMBER 
these scales that the spur shoot of the needles arises. After it 
has developed a few scale leaves and a tuft of needles, this spur 
shoot generally remains dormant. If, however, the terminal bud 
of a branch happens to die; these lateral shoots may grow into a 
normal branch, bearing at first isolated juvenile green leaves and 
then scale leaves with spur shoots in their axils (fig. 8). 
VARIATIONS IN THE NUMBER OF NEEDLES.—The number of 
needles on the spur shoot of each species is considered constant 
enough to be used as a character for classification; still, on rejuve- 
nated or infected twigs, shoots are found which bear an unusual 
number of needles. Boopie (1) makes the following statement: 
“In Pinus monophylla the spur shoots as a rule bear each a single 
needle, but two are occasionally present. Masters found by 
studying early stages that two leaf rudiments are always produced, 
but that one of them generally becomes arrested at an early stage.” 
Single needles have been observed by BooptE on P. Laricio, 
and we found some on twigs of P. maritima that were infected by 
the larva of a xylophage insect (Hylesinus piniperda). These 
single needles are roughly cylindrical; in many cases a groove is 
present on one side of the leaf. On following it downward, it is 
found to contain two papillae, one of which is the apex of the spur 
shoot, the other the rudiment of the second needle. Variation 
in the number of needles in this case is due to arrest in the develop- 
ment of one of them. It is a rare occurrence in P. maritima and 
P. Laricio, but it has become the rule in P. monophylla. The 
multiplication of needles on the spur shoot has often been recorded 
on wounded, infected (13), or vigorous (20) shoots, and it has been 
regarded as a reversion toward ancestral, many-leaved gymno- 
sperms (3). 
_ Although these variations are somatic in origin, we have proved 
that they comply with Mendel’s law, in that the proportion of bud 
mutations on the shoot is precisely that of F, recessives in the case 
of hybrids. Shoots of vigorous P. maritima or those infected with 
Coccus resinifians have been observed to yield 75 per cent normal 
2-needled spur shoots, and 25 per cent 3-needled spur shoots. 
Proliferating spur shoots on P. virginica in Arcachon often yield 
75 per cent normal 3-needled spur shoots, and 25 per cent abnormal 
