NEW CELL FORMATIONS IN PLANTS 275 



LXXIII, Fig. 9). In the fibers there are pits of a special form, similar 

 to those found in other members of this family. They are called by 

 Solereder (7) ''Bordered Pits." In form they are circular, the wall 

 being here rather heavily thickened. The central pore is slitlike, and 

 the direction of the slit on one side is generally the reverse of that on 

 the other, causing under low power the appearance of a cross (Plate 

 LXXIII, Fig. 9). This is more evident in the smaller pits, where the 

 slits cross each other at right angles, than it is in the largest ones, the 

 larger slits seen in these crossing more obliquely. 



The Medullary Rays are very narrow, generally being but one cell 

 wide (Plate LXXII, Fig. 5). In passing thru the bark they cross directly 

 thru the hard-bast strands. The walls of the cells become lignified, 

 and have many simple pits in them. 



The Phloem is of two sorts. Some of the cells are soft, in cross- 

 section somewhat rectangular, and in longitudinal section about twice 

 as long as broad. There is a secondary differentiation of these into 

 some that contain much tannin and into others that are comparatively 

 free from it. The tannin may be demonstrated by treatment with 

 ferric chloride in the usual way. In position the tannin cells may be 

 scattered, or they may form long rows two or three cells wide and circhng 

 the stem for a considerable distance. One or two of these rows (rarely 

 more) may lie in the ordinary soft bast between the hard-bast strands 

 of one year and those of the year preceeding. Many of the soft-bast 

 cells contain conglomerate crystals. 



The other type of phloem or bast cell is lignified, and forms in the 

 older regions of the bark plates or strands of hard-bast cells. These 

 form each year a broken ring encircling the stem. The size of these 

 hard-bast strands varies considerably, altho they are fairly uniform 

 in thickness in any one year's ring. Around the margin of each 

 strand is a layer of cells containing tabular crystals. Stone-cells fre- 

 quently appear, and their presence cannot be attributed to any special 

 injury to the tissues. They are not distributed in any regular manner. 

 The Cortex seemed to be largely gone from the specimens examined, 

 but when it was present it showed a ring of sclerenchyma embedded 

 in the soft parenchyma. The outer cortex in young stems consists 

 of a collenchyma. Under the lenticels there are formed wedge-shaped 

 areas with the cells rounded instead of rectangular as is usual elsewhere. 

 Cork forms early. According to Solereder the cambium originates 

 from the outer layer of cortex cells. In the particular variety of Chestnut 

 studied, the surface of the bark remains smooth for a number of years, 



