PINE NEEDLES, THEIR SIGNIFICANCE AND HISTORY 
JEAN DUFRENOY 
(WITH TWENTY-NINE FIGURES) 
Are pine needles shoots or leaves? The question may still be 
debated, since neither the shoot nor the leaf has as yet been clearly 
defined. A review of the morphology, development, and physiology 
of the “needles” may be of interest. 
Morphology 
The definition given by VAN TIEGHEM (21), and usually adopted, 
is as follows: The leaf is symmetrical on both sides of a plane; the 
shoot is symmetrical around an axis. A needle is symmetrical on 
both sides of a plane, not around an axis; but by bringing into 
contact the different needles grouped at the end of a spur shoot, an 
organ is obtained which is symmetrical around an axis, and which 
therefore is a shoot. Needles, therefore, are fragmentary shoots. 
Anatomically they are polystelic shoots which have divided 
longitudinally into a variable number of parts" in order to increase 
the surface available for carbon assimilation. Being fragmentary 
shoots, the needle may be considered the homologue of the petiole 
of broad-leaved gymnosperms. The anatomy of the needle is 
strikingly similar to that of the petiole in Ginkgo, and we may quote 
COULTER (4) as follows: ‘‘The most ancient gymnosperms pos- 
sessed ample fernlike leaves... . . The conifers, however, have 
developed a very different type of leaf . . .’. which reaches an 
extreme expression in small and rigid needles.” 
The derivation of needles from fernlike phyllodes is apparent 
from anatomical data. 
* That the different needles of a spur shoot are parts of the same organ is often 
strikingly evident. In most cases when a needle bends, the others bend also, so that 
all can be grouped into a cylindrical, though bent, shoot. When solitary, at the end 
of a spur shoot, needles are roughly cylindrical in form and shootlike, as normal 
needles of P. monophylla, and abnormal needles of P. Pumilio (STRASBURGER), 
P. Laricio (BoopLe 1), and P. maritima (DUFRENOY 13). 
439] (Botanical Gazette, vol. 66 
