450° BOTANICAL GAZETTE [NOVEMBER 
case for the stamens and scales of pines, in which resin is excreted 
from the epidermal secreting cells. In juvenile leaves most 
epidermal cells become sclerenchymatous (to protect the paren- 
chyma), and a very few still secrete resin (figs. 22, 23). Internal 
organs then differentiate, which can store resin, so that paren- 
chymatous cells do not get poisoned, and resin canals run from the 
needles to the shoot and into the roots. The possibility of getting 
ay — 
MODIO- 
Fic. 25 Fic. 26 
Fics. 22-26.—Fig. 22, abnormal juvenile leaf showing secretory hair (¢) on ven- 
tral face; fig. 23, abnormal needles showing rudimentary secretory hair () on ven- 
tral face; fig. 24, scale leaf: strikingly similar to scale of Cycas; the hairs may be 
interpreted as sterilized ancestral ovules or stamens: fig. 25, juvenile leaf, showing 
hairs that may be interpreted as ancestral stamens, now sterile and secretory; 
fig. 26, secretory hairs of scale leaf (left) and juvenile leaf (right): s, secretory hair; 
é, epidermal cell. 
rid of refuse poisonous material probably explains why coniferous 
trees are evergreen, whereas most of the other trees periodically 
lose their leaves and rest in winter. 
Pathology 
The needles of Pinus maritima may last 5 or 6 years. ae 
their death must be due to an accident, either a general trouble 
in the nutrition of the tree, or a local infection by rust or smut. 
