442 BOTANICAL GAZETTE [JUNE 
The primary lenticels are always formed directly beneath the 
stomata, following in this respect the general rule first enunciated by 
TRECUL. Some of the lenticels never break through the epidermis 
but remain in an undeveloped condition. The lenticel phellogen 
arises from the layer of cells just within the epidermis. The thin- 
_ walled complementary cells are at first closely packed together. 
After about twelve layers of these cells are formed the epidermis is 
ruptured, and the complementary cells as they become exposed sepa- 
rate from each other and present very irregular and distorted outlines. 
The mature lenticel agrees with the second of the types described by 
Devaux‘ and shows no distinct layers of cork among the. comple- 
plementary cells (jig. &). In some 
cases, however, a lenticel contains a 
few scattered stone cells (fig. 8, st). 
Secondary lenticels are developed from 
secondary phellogens and make their 
appearance in the splits of the bark. 
These lenticels break through the 
gt 
Pig.ic: 
*i 
[| 
i 
OS 
é OY 
ERS 
we 
(f 
ef 
A 
O 
eo <a eVox Ss : 
Sie Ogely es 
FIG. 9. ere ee 
Fic. 8.—Section through a primary lenticel. X55. Fic. g.—Section through @ 
secondary lenticel. X60. c, cork; com, complementary cells; e, epidermis; ~, paren- 
chyma; phel, phelloderm; sc,, primary sclerenchyma; st, stone cells. 
layers of cork and parenchyma cells which enclose them and eventu- 
ally exhibit the same structure as the primary lenticels (fig. 9). 
Since the primary cork phellogen is a direct extension of the lenti- 
cel phellogen, it is never epidermal in origin but is always derived 
3 Compt. Rend. 73:15. 1871. 4 Ann. Sci. Nat. Bot. VIII. 12:61. 1900- 
EE 
