PLATE 46 
i» 2.—Cross sections of the killed tissue (pith) at one side of the proliferations shown 
on Plate 5. Above in each are rows of collapsed dead pith cells containing many crys¬ 
tals of calcium oxalate. Below are tissues which have proliferated from the inner face 
of the bundle sheath. Below at the left, in figure i, bundle vessels are included. In 
figure 2, which joins on to the right of figure 1, the section cuts above the vessels of the 
bundles. In the middle of each section immediately under the killed (black) tissue (at 
XX) are vessels, and at P a little mass of tissue interpreted as new phloem, but no sieve 
plates were found in it. This phloem and the new xylem vessels must have formed in 
advance of the death of the tissues surrounding it (it was not itself dead tissue) and 
further growth stopped by the deeper killing in of the pith tissues. A similar small 
mass of phloem (also subtended by spiral vessels) is visible in the same relative posi¬ 
tion in sections made from the other side of the proliferations shown on Plate 5. This 
is, I believe, the interrupted beginning of a second xylem-phloem ring. X160. 
3.—Cross section of cauliflower leaf, showing intumescences formed after exposure 
to vapor liberated from one-half gm, of secondary methylamin chloride by adding 
10 c. c. of a 15 per cent solution of sbdium hydrate. A free-hand unstained section 
of one of the intumescences shown on Plate 62. Time of exposure to the vapor, 30 
minutes. Temperature, i8°C. Date of collection, nine days after exposure. The 
section shows local thickening of the tissues with destruction of the chlorophyll. The 
dark parts of the section were green. X75. 
