S4 
Walter Gaudineu. 
the acid, much less washing with water is liable to cause verv sensible 
displacement of tbe tissue. In the case of resistent middle lamellae these 
structures swell and stain. Again my results as lo the action of Carmine, 
whether Ammonia or alum Carmine, point lo the fact that it bas but litlle 
selective powers, slaining at tbe same time l)otb the protoplasm and the 
cell-wall, and I therefore am forced to regard it as unsatisfactory for such 
an investigation as the present. Finally where one relies on the fact of the 
elinging of the protoplasmic processes entering the pits, to the pil-membrane, 
it is a mistake to use either alcohol material or a razor wetted with alcohol 
since by so doing the protoplasm is rendered rigid and brittle, and it can 
neither be drawn out into Strands, nor will it adhere to the mcmbrane when 
any appreciable tension is set up. 
I therefore worked overMr. Hiixhousk s results with the greatest possible 
care. I may state at the oulset that the material he employed is in many 
respects extremely favourable, bolh on account of the conspicuous develop¬ 
ment of the pits, the comparative thickness of the pit-membrane and the 
non resistent character of the middle lamellae. In this respect bolh Prunus 
and Acer deserve especial notice. 
Naturally Mr. IIii.uiouse’s view of a direct continuity necessitates the 
exislence of a small Perforation in the pit-membrane. Wliat strikes one at 
first on looking over bis figures of Prunus is that if figure 4 which represents 
two somewhat swollen processes on opposite sides of the pit united by a 
sieve-structure Iraversing the pit-membrane, be true, and if he obtains such 
a structure by the cautious and regulated action of Sulphuric acid, how is 
it that when the acid has been allowed lo act for a much longer time, he 
obtains the appearance of direct continuity, unless indeed we are to sup- 
pose that both means of communication are present in one and the same 
tissue. But on the whole, one is led to infer that the direct continuity is the 
typical structure. 
In order to examine the matter for myself 1 thoroughly investigated the 
structure of the cortical tissue of the base of the leaf, and of the stem, in 
Prunus, Ilex, Acer, Aesculus and Aucubci Japonica which bitter is perhaps 
the best material of all. I found that after the lengthy action of the acid, 
the difficullies attending manipulation and observation were verv great. 
After a treatment of 24 hours with Sulphuric acid, 1 found that very thin 
sections were usually so disintegrated and displaced as to prevent any satis- 
faclory examination of them. The thicker sections are more resistent, and 
on the whole the protoplasm withstands the action of the acid, much beiter 
than one might expect. In many cases the processes are almost entirely 
dissolved, and the protoplasmic bodies present a spherical form, having 
projecting l'rom them at certain points a few extremely short protrusions. 
In other instances the processes remain fairly intact, their apices ending 
bluntly in a somewhat swollen rounded extremity as Mr. llu.uioisi; has 
