i8o 
Notes . 
chouc, which in their physical and chemical properties absolutely 
resemble the contents of the caoutchouc-cells (and are similar to the 
caoutchouc of Hippocrateaceae). 
F. E. FRITSCH. 
Jodrell Laboratory, Kew. 
ON LIGNIFICATION IN THE PHLOEM OP HELIANTHUS 
ANNTJUS. — An examination of the structure of two plants of the 
common sunflower grown at Kew last year has yielded one or two 
results, which do not appear to have been previously recorded, viz. the 
occurrence in this plant of: (i) sieve-tubes and companion-cells, whose 
walls ultimately become lignified; and (2) sieve-tubes and companion- 
cells, whose contents give reactions resembling those of lignin. 
One of the plants was cut down and put into spirit in August, when 
it was already forming fruit; the other plant was allowed to grow 
until early in October. In the thicker parts of the stem of the first 
plant, patches of the medullary-ray-cells in the phloem were lignified. 
A few sieve-tubes with slightly lignified walls were found. In the 
second plant the stem had attained a diameter of an inch and a half 
near the base and for some distance upwards. In parts of this thick 
region, lignification of the walls had taken place in the whole of the 
pericycle, in the larger and many of the smaller medullary rays in 
the phloem, as well as in several of the small strands of sieve-tubes 
and companion-cells occurring in the outer region of the secondary 
phloem between the primary bundles, and in a fairly large block of 
sieve-tube-containing phloem on the inner side of each primary 
sclerenchyma-strand. The small strands were examined in transverse, 
radial, and tangential sections, and it was found that fairly frequently 
some, and occasionally all the sieve-tubes and companion-cells com- 
posing them possessed lignified vertical walls. In some cases the 
sieve-plates were covered with callus, and not lignified ; in others they 
were destitute of callus, and lignified. Lignification of the walls was 
frequently seen in the single or paired sieve-tubes with companion- 
cells, which run horizontally or obliquely through the medullary rays, 
and form tangential connexions between the vertical strands of sieve- 
tubes, as in Vitis vinifera , See. Lignification of elements (sieve-tubes, 
companion-cells, and parenchyma) bordering the large, still unlignified 
phloem-masses, corresponding to the primary bundles, suggested a 
