356 YOUNGKEN— ON THE MYRICACEAE 



Myrica Gale, L. (Plate 86, Fig. 17.) 

 In passing from periphery toward the centre, the following structures 

 are to be observed. 



1. Cork of several layers of elongate brick-shaped cells which are 

 unevenly stained and whose walls are partially lignified, in part suberized. 



2. Cork cambium of tangentially elongate meristematic cells. 



3. Cortex of a few layers of tangentially elongated parenchyma 

 cells with small angular intercellular air-spaces. Most of the cells of 

 this region contain starch and tannin, many possess conglomerate and 

 monoclinic prisms of calcium oxalate, while a few have their cell walls 

 thickened and contain gummy lignin. No sclerenchyme elements are 

 present. 



4. Endodermis whose cells do not differ materially from those of 

 the adjacent cortex. 



5. Phloem which is comparatively narrow and composed solely of 

 sieve tubes, companion cells and phloem parenchyme. The primary 

 medullary-rays in this region are broadened out in fan-shaped manner 

 and show a width of 1-5 rows of cells. 



6. Cambium of thin walled tangentially elongated cells. 



7. Xylem which is very compact in nature showing fewer tracheae 

 than in any other Myrica root found in the Northeastern states. Most 

 of the tracheae are distinctly polygonal and form interrupted rings in 

 the spring wood. (Plate 86. Fig. 17.) Their walls show transverse 

 pits which are usually arranged in longitudinal rows. The greater 

 part of the xylem consists of tracheids which are square in transverse 

 section. The primary medullary-rays are 1-4 rows of cells wide and 

 are always four in number. They are arranged in a cruciform manner. 

 The secondary medullary-rays are 1-2 rows of cells wide. Both kinds 

 of medullary-rays contain numerous spheroidal starch grains. Tannin 

 is found in considerable quantity in the cortex, phloem and medullary 

 rays. 



Comptonia asplenifolia, (L.) Alton. (Plate 86. Fig. 18.) 



This root presents the following characteristics: — 



A cork of several layers of reddish-brown, brick-shaped cells whose 

 walls are for the greater part suberized. Beneath the cork is found a 

 phellogen zone of somewhat tangentially elongated cells which cut off 

 cork in an uneven manner. 



The cortex is comparatively narrow and is composed of tangentially 

 elongated parenchyma cells, most of which contain starch, some rosettes 



