PROTOPLASM THROUGH THE WALLS OF VEGETABLE CELLS. 
841 
Thus Phytelephas or Lodoicea require a strong solution of iodine, while Ruscus or 
Colchicum will quickly assume a dark yellow with a solution of a comparatively weak 
strength. Treatment with sulphuric acid was also resorted to, not only as an alterna¬ 
tive method, but also for the purpose of confirming my results with pulvini; although, 
from the very great thickness of the walls and the consequent enormous swelling which 
occurs, it was found that, as a rule, Chlor. Zinc Iod. was the preferable reagent for 
ordinary use. 
On repeating the observations already made upon Strychnos Nux-vomica my results 
fully confirmed those of Tangl and Strasburger in every particular ; and in thin and 
•carefully-prepared sections it can be plainly seen that the threads do cross the middle 
lamella. Like Tangl, I was unable to stain the threads with reagents in the usual 
manner; and, in consequence, I instituted those experiments which led me to adopt 
that particular modification of dissolving Hofmann’s blue in picric acid, and using it 
as a stain, which I have already dwelt upon in the earlier part of this paper. When 
by the use of alcohol the extreme swelling which takes place upon treatment with 
water is prevented, sections may be stained with picric- Hofmann’s blue, and after 
mounting in strong glycerine may be successfully observed. 
With regard to Strychnos 'potatorum , I am disposed to agree with Strasburger 
that a sieve-plate-arrangement does exist between the pits, for a striation could 
certainly be made out. However, the seeds I had to work upon were extremely old, 
and as such I look upon the results obtained with them as unsatisfactory. 
As regards the structure of Phoenix dactylifera, when treated with iodine and Chlor. 
Zinc Iod. I came to the same conclusions as Professor Strasburger'" that, although 
a striation could be observed, the threads were not nearly so clear as Tangl’s drawing 
represents, and, indeed, were made out with difficulty. After treatment with sulphuric 
acid, washing, and then iodine-staining, they were defined much more clearly; but the 
best and in every way most satisfactory results were obtained by staining the washed- 
out sections with Hofmann’s violet and glycerine. In the latter case the stained 
protoplasm was contracted, and running through the pit membrane could be seen well- 
coloured threads presenting a distinct sieve-plate-arrangement (Plate 69, fig. 13). 
In the same way Areca oleracea, usually known as Euterpe oleracea, at first gave a 
very feeble result when treated in the usual way ; but, after a great number of trials 
and the use of strong iodine, and a prolonged action of Chlor. Zinc Iod., delicate 
threads could be plainly observed, which, moreover, appeared to cross the little 
developed middle lamella. 
Having obtained the above-named results I commenced the examination of a 
number of palm seeds and of other seeds possessing a similar structure, in the hope of 
being in the end able to make some statements as to their general histology and to 
determine how far such a structure was of general occurrence. The following is the 
list of the palm seeds examined. I am indebted to Sir Joseph Hooker for kindly 
* Loc. cit. 
