364 YOUNGKEN— ON THE MYRICACEAE 



3. Cortex generally broader than corresponding region of M. cerifera 

 of same age. Its cells are tangentially elongate and contain either starch 

 grains, gummy lignin or crystals of calcium oxalate either in the form of 

 rosette crystals or monoclinic prisms. The intercellular air-spaces are 

 generally somewhat larger than those of the cortex of M. cerifera aerial 

 stem and frequently contain several crystals lying in a row one above the 

 other. Stone cells are quite numerous and scattered either singly or in 

 groups throughout the cortical parench}Tne. 



4. The pericycle shows a broken ring of sclerenchyme elements. 

 These are for the most part considerably narrower than those in the 

 stem of M. cerifera. 



5. The phloem is uniformly narrower than the similar region of 

 M. cerifera. Through it run numerous medullary-rays. The phloem 

 elements are smaller than those of M. cerifera. Many of the phloem 

 cells contain rosettes or monoclinic prisms of calcium oxalate. Tannin 

 is also present in large amounts Few bast fibres occur in this region. 



6. The cambium line is much less wavy than that of M. cerifera. 



7. The xylem consists of numerous tracheae containing Actinomyces 

 forms intermingled with many woody fibres and comparatively fewer 

 wood parenchyma elements The tracheae are generally narrower than 

 those of M. cerifera aerial stem. The largest have a measurement of 

 38.4 jjL across, similar to the largest in the aerial stem of M. cerifera. 

 The autumn wood is almost wholly composed of greatly thickened woody 

 fibres which collectively form a band in each annual ring fully twice as 

 wide as that observed in M. cerifera. (Plate 87, Fig. 21.) 



The medullary-rays are thinner than those of M. cerifera. This is 

 not due to fewer rows of cells in these structures but rather to the fact 

 that the cells are smaller and narrower. Like those of M. cerifera the 

 medullary-ray cells of the xylem have their walls more or less lignified 

 and serve for the storage of starch. The primary medullary-rays are 

 mostly 1-5 cells wide, the secondary 1-2 and 1-3 cells wide. 



8. The pith is composed of active polygonal to rounded cells, whose 

 walls are lignified. They serve for the storage of starch. Some fre- 

 quently contain gummy-lignin. 



Subterranean branch of Myrica Carolinensis, Miller 



There are fewer layers of cork formed than in the aerial stem. The 



cells of the cortex are somewhat larger, more rounded and contain more 



starch. The intercellular air-spaces between cortical parenchyma cells 



are larger and devoid of calcium oxalate crystals. The sclerenchyme 



