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Lenticels. 
An excellent popular article on lenticels entitled, " How the bark breathes " will 
be found in the Journal of Heredity (Washington, U.S.A.), loth November, 1915. p. 490. 
It points out that in connection with the elaborate respiratory system of plants connected 
with the taking in of air and giving out of carbon dioxide we have three general types 
of external openings, viz. : 
1 . Stomata or valves on the surfaces of leaves and young shoots. 
2. Ventilating pores, which occur in certain aerial roots. 
3. Lenticels, pores in the older wood, whose presence can be noted by the unaided 
eye in almost any plant. 
The earlier naturalists were quite in the dark as to the functions of these pores. Guettard, who 
described them in 1745, designated them merely as glands; De Car.dolle (1826) thought they were a kind 
of bud, from which roots later put forth; Unger (1838) believed they had something to do with repro- 
duction ; but as early as 1809, Dupetit-Thouars declared their purpose was ventilation, and the work of 
several students during the next half century demonstrated that this opinion was well founded. 
It has been found that lenticels are in some plants functionless, some for a season 
of the year ; others are permanently closed, and of no value to the plant for breathing. 
Following are the legends to two admirable photographic illustrations to the 
above quoted paper : 
The ventilators of a rose Iteig. The irregular openings or ' eruptive craters ' in the bark, photo- 
graphed under high magnification, are known as lenticels, and serve as pores through which air is admitted 
to the inside of the plant. By channels and passages of various kinds between the interior cells of the 
plant, the air passes to even the most distant parts. The plant is thus enabled to renew its supply of 
oxygen, and at the same time it, discharges carbon dioxide through the lenticels. 
Tirig of a Chinese Magnolia, highly magnified. The dry, powdery cells which fill the breathing 
pores of the bark have absorbed moisture from the air until they have swelled out and protrude like warts. 
One of the functions of the lenticels is to regulate the transpiration of moisture between the interior of the 
tree and the outside air. 
The author (unnamed) of the paper includes the following comment : 
These facts have led many plant physiologists to think that, although the lenticels undoubtedly 
do fulfil in many cases the function of breathing pores for the bark, that is not really their purpose. Such 
a solution of the problem accords well with the interpretation of nature of certain scientists, who hold on 
philosophical grounds that nothing should be said really to have a purpose. (I.e. p. 492). 
Those who desire to pursue the subject further are invited to peruse " A Text- 
book of Botany " by Coulter. Barnes and Cowles, Vol. II, Ecology, p. 660, under the 
main heading, " Carbohydrate synthesis and aeration in stems," and the sub-headings, 
" The structural features of lenticels," " The causes of lenticel development," ' The 
role of lenticels." In regard to the last, they say (p. 663) : 
Lenticels are regions of gas exchange, taking the place of stomata in stems after the inception of 
secondary growth, and making possible the continued activity of the chlorophyll after cork formation has 
begun. Only a somewhat, structureless organ such as a lenticel, consisting of an indefinite patch of loose 
cells, is fitted for gas exchange in bark, whore growth and rupture occur continually. 
At figure 974 is a clear photograph showing the markings with which we are 
familiar in Birch (Betula) bark, which consist of numerous transversely elongated 
permanent lenticels. 
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