IV. On the conlinuity of Ilie protoplasm through the Walls of vegetable cells. (jj 
In structure the typical pulvinus eonsisls of an axial vascular bündle 
which is surrounded by some eight layers of parenchyma colls. The vvliole 
organ is invested by a feebly developed epidermis and the parenchyma 
cells are very conspicuously pitted especially on their longitudinal walls. 
I studied in detail the pulvini of Mimosa pudica, Hob inin pseud-acacia , 
Amicin zygomerts and Phaseolus multißorus, of which Mimosa gave the best 
resulls. Thin longitudinal sections of a fresh pulvinus of Mimosa are cut in 
Water, treated wilh Sulphuric acid, and stained as already described. Then 
'f the Operation has been successfully accomplished, the cell-walls will 
have undergone considerable swelling so as to he rendered almost invisible, 
and the protoplasmic bodies will present the appearance of a number o'f 
deeply stained irregularly shaped masses lying in the swollen substance er 
the cell-wall. From these main protoplasmic. masses radiate numerous pro- 
cesses towards the pits, and in any two neighbouring cells the processes 
from the one central mass are exactly opposilc those proceeding front the 
other, thus presenting a tnosl characteristic appearance and resembling 
somewhat a preparalion of corneal conuective tissue which has been stained 
With gold Chloride. 
The appearances I have described are the natural outcome of the action 
ol Sulphuric acid upon fresh sections of vegetable tissue and the whole 
process may be watched under the microscope. It will then be apparent 
thal the following ellects are produced. The protoplasm is almost immedia- 
tely killed, and in Iltis process, allhough some sliglit conlraction may lake 
place, it remains for the most pari perfectly passive. The cell-wall rapidix 
conunences lo swell and in so doing drives before it the passive protoplasm, 
''hielt in virtue of its previous vacuolation easily admits of being squeezed 
,nt0 a much smaller space. The ellect of Ute swelling wall, as far as the pits 
*<ie concerned, is to cause a narrowing of the diameter of the pit-cavity, 
"hile the closing membrane itself swells but little. The processes front the 
general cell-protoplasm which enter the pits are left in their normal posilion, 
jdthough they are necessarily somewhat constricted, and, what is a remar- 
«»ble facl, that portion ol each process which immediately abuls on the pit- 
closing-membrane, usually slicks lo the latter structure, and is hehl in 
Position even though owing to the swelling of the cell-wall, a verj appre- 
ciable tension ntay be set up and the processes may be drawn out inte 
Strands of great tenuity. In other instances, and especially when the action 
° 1 ’ 1,10 acid has been prolonged, the processes contract away from the closing 
'Oentbranes altogether. The narrowing of the diameter of the pit-cavity 
Naturally assists to maintain the processes in posilion in a merely ntechani- 
Cal manner, but apart from Ibis one can recognize w ith ease that the apices 
0f ,lle protoplasmic processes adhere with considerable tenacity to the clos¬ 
art membianes of the pits. For the satne thing occurs in thin walled tissue 
'here the narrowing of the pit diameter is inappreeiable, and where moreo- 
