286 BOTANICAL GAZETTE, | [ November, 
they form the main branches of the crown, begin, when 
young, to develop wings in the ordinary manner, and con- 
tinue doing so for six or eight years. Then on the older in- 
ternodes the development under the wings becomes less and 
less in amount; the ordinary periderm acc mmouates itself 
to the increasing size of the surface of the other parts of the 
stem, that under the wings apparently remaining stationary, 
until it is highly probable in many cases the growth of the 
wing entirely ceases and the phellogen of the entire circum- 
ference resumes its function of uniform growth, and the wings 
are slowly cracked off. However this may be, many of the 
larger stems appear to be covered with a nearly smooth per- 
iderm, and many others are nearly smooth at the place where 
they join the main trunk, while further on toward their ex- 
tremities they are profusely covered with wings. : 
ow taking the growth of the main stem from its origin, 
a young tree, three years old, was cut off about one and a 
half feet from the ground. At this height the circumference 
was nearly covered with the cork wings, but by looking care- 
fully it could be seen there was still a distinct longitudinal 
strip or band which was yet free from this growth except 
under the lenticels. This was more and more easily traced 
est internodes of this year’s growth; date, July 16. The 
whole length of this year’s growth of main stem was 
forty-six centimeters; the lower thirteen centimeters had 
well-developed cork wings, above this none had yet ap- 
peared. Lateral branches growing out from this portion of 
the main stem were also supplied with wings on their older 
internodes. It is easy to see how the whole bole of the tree 
probably becomes covered with its ridged and furrowed per- 
iderm. In the tree just described, the longitudinal strip or 
band along which ran no regular wings was already supplied 
with corky tissue at the lenticels, raising these slightly from 
the surface. The phellogen cells of this tissue probably soon 
after the third or fourth year become endowed with special 
activity ; the layer is extended from lenticel to lenticel, just 
as in the first year’s growth, till at last connected ridges are 
