380 YOUNGKEN— ON THE MYRICACEAE 



24.28 jux 12.14 m. Stomata are scattered amongst the lower epidermal 

 cells without order. Each in the mature adult leaf is surrounded by 

 6-8 neighboring cells. Crypts are more numerous than on the upper 

 epidermis. These contain similar glands to those found on the upper 

 surface. Very few 1-celled trichomes or their bases are ordinarily found. 



Myrica Carolinensis, Miller. 

 The upper epidermis of this leaf consists of polygonal cells, whose 

 outer walls are covered by a thin cuticle. The vertical walls are recti- 

 linear. Over the veins the cells are rectangular and elongated in the 

 direction of the bundles. The cells are filled with a brownish substance 

 as in M. cerifera and M. Macfarlanei. Their mean dimensions are 29. 13 /x 

 X 17 M- Scattered over this epidermis are numerous simple unicellular 

 trichomes with sclerotic bases, as well as the bases of sclerotic hairs, 

 each of which is surrounded by several rows of cells arranged in radial 

 fashion. Very few or no golden yellow glandular trichomes are found. 

 These are more frequently present than absent. Each consists of a 

 stalk and a gland or head. The stalk is 4-7 cells in length and two rows 

 of cells wide. The gland is balloon-shaped. The glandular trichomes 

 are inserted into the epidermis at the bottom of crypts which are less 

 numerous on the upper than on the lower surface. 



The mesophyll, as in the leaves of M. cerifera, shows dorso-ventral 

 differentiation into palisade and spongy parenchyma regions. The 

 palisade zone consists of 2-3 layers of loosely arranged columnar shaped 

 cells, some of which contain rosettes or monoclinic prisms of calcium 

 oxalate. The spongy parench}Tiia region comprises a network of oval 

 to irregular shaped cells arranged in chain fashion and surrounding large 

 intercellular air spaces. Some of these cells contain crystals of calcium 

 oxalate. The fibro-vascular bundle of the mid-rib and smaller veins 

 course through this region. The stronger veins are united to the upper 

 epidermis by means of hypodermal elements which are coUenchymatic. 

 Other veins are united to both epidermises by hypodermal cells contain- 

 ing crystals of calcium oxalate. The fibro-vascular bundle of the mid- 

 rib is surrounded above and below by an arc of sclerenchyme, the upper 

 arc as in M. cerifera being the more strongly developed of the two. 



The lower epidermis consists of wavy walled cells which have the mean 

 dimensions of 28.02 m x 14.4 m- Numerous stomata occur on this 

 epidermis. These are surrounded by 5-6-7 neighboring cells. Crypts 

 are numerous and scattered without order over the lower surface. Each 

 contains a golden-yellow balloon-shaped gland subtended by a stalk 



