191«] Hall-Goods peed: Chnjsil 241 



figure 3, illustrates the statements made above as to the conspicuous 

 staining of the cortical ray extensions and the presence of rubber in 

 the phloem and rays. It will be noted that the portions of the rays 

 lying in the first annual increment contain relatively negligible 

 amounts of rubber as compared with the portions of the rays lying 

 in the second and third year xylem. The line " C " marks the approx- 

 imate limits of the living cortex. 



Figure 2 in plate 18 is included to show the extent of the rubber 

 bearing tissues and of the non-rubber bearing cork and barky 

 elements. The "A" line indicates roughly the external limits of the 

 rubber bearing cortex. Cork has formed below this line but the 

 primary cortical tissues cut out thereby show rubber not yet entirely 

 disintegrated. The "B"-line points to the tangential strip in which 

 maximum (quantities of rubber occurring in the cortical parenchyma 

 and in the cortical ray extensions may ordinarily be expected to 

 occur. Figure 2 is a cross section of a five year old stem. 



In plate 19 the two cross sections give evidence as to the distribution 

 of rubber in mature stems. Figure 1 was cut from a six year old 

 stem and figure 2 from a nine year old stem. The greater portion 

 of the bark and inner cork is absent in figure 1 and it will be seen that 

 the cortical ray extensions filled with rubber extend outward for a 

 long distance. The broad ray extension on the extreme left in figure 1 

 is characteristic of many of the cortical extensions of the primary 

 rays and its cells are densely packed with rubber. 



Figure 2 in plate 18 shows a particularly thin section from which 

 in places the rubber inclusions have fallen or have been washed out. 

 Line "A" indicates roughly the limits of the rubber bearing tissues; 

 those external being composed largely of cork and bark. 



We have found that rubber is present in the cell either in what 

 may be spoken of as a '' diffused "" state or in the form of globules. 

 In the difl'used state the entire cell cavity is filled with a mass of 

 stained substance which appears to be somewhat homogeneous. This 

 condition is shown in certain of the cells in plate 18, figure 4, the 

 spherical globules representing detached masses of rubber which have 

 rounded up when free from the cell wall. When present in globular 

 form, one or more large spherical globules partially fill the cell cavity 

 or a number of smaller definitely spherical globules are distributed 

 without apparent arrangement within it. Spherical globules in situ 

 are shown in a number of the cells in plate 18, figure 5. For a time 

 it seemed possible that the form in which the rubber occurred in the 



