THE ROOT-SYSTEM ОЕ IMPATIENS ROYLEI. oll 
Raphid sacs occur in the pith and less frequently in the cortex. 
What are most probably tannin cells are very common in the adventitious 
roots». These cells vary in colour ; they may be yellow, light brown to darker 
brown, reddish brown, or in some cases they have a greyish tinge. They 
appear in the outer half of the cortex and also in several of the epidermal 
cells simultaneously with the development of cork. А few isolated cells or 
pairs of cells of this nature occur in the pith, but these are always less 
obvious and are of a paler colour, In no cases are these cells found while 
the root-hairs still persist, and in only very few cases do they appear in young 
or old subterranean roots. They reach their fullest development in the stout 
abortive roots, with a considerable quantity of cork, which arise from the 
lateral branches. 
Microchemical tests for tannin were, however, somewhat inconclusive, but 
the following reactions may be noted :— 
1. The cells stained deeply with methylene blue. This test is incon- 
clusive since mucilaginous contents react similarly. 
2. In some cases the cells became very slightly darker upon being 
treated with ferric chloride, but the general results were far from 
convincing. 
3. The potassium dichromate test gave a negative result. 
4. The lead acetate test gave a negative result. 
The ammonium chloride and ammonium molybdate test gave a 
Qt 
negative result. 
Cells of an identical appearance occur in the pith and cortex of the stem 
and give the reactions for tannin. This, together with the fact that the cells 
are almost always absent in subterranean roots, seems to indicate that the 
aerial roots contain tannin, even though it be but feebly developed, and 
further support may be adduced from the fact that tannin cells occur in 
Impatiens Sultani, Hook. f.*, so the feature is not exceptional in the genus. 
Rootlets from adventitious roots. 
An adventitious root upon entering the ground, or as the result of injury, 
sends out numerous lateral roots. Of these, fifty were examined, with the 
following results :— 
Number of root poles ..... TOPPED 3 4 5 6 7 8 12 
Number of specimens ............ ,,.6 2014 5 3 1 1] 
Rootlets are rarely developed except under the two conditions mentioned 
above, but occasionally traces of them are found т uninjured aerial roots ; 
they then arise about the junetion of the broad and narrow regions 
(text-tig. 180). 
* Solereder, ‘Systematic Anatomy of Dicotyledons.' 
