366 MR. 8. LE M. MOORE’S STUDIES 
plenty, (ii.) with traces, and (iii.) with no signs of starch in the. 
chloroplasts of their epidermis; consequently the movements 
of the latter are not dependent upon their capacity for assi- 
milation. 
If the objection were raised that the. argument here used, 
when carried to its logical conclusion, would militate as strongly 
against Sachs’s view, that the cause of photolysis is to be referred 
exclusively to the movements of protoplasm, the answer would, 
it is apprehended, be somewhat as‘ follows :—It is true that the 
epidermal cells, having in most species a nucleus, a protoplasmic 
- reticulum, and chloroplasts, do not differ in any essential feature 
from ordinary cells ; but itis no less clear that, whether from an. 
originally small supply or from the great stretching undergone, 
the relative quantity of protoplasm contained in them is very 
small. In my previous memoir the dependence of photolysis 
upon protoplasmic momentum on the one hand, and inertia of 
the chlorophyll on the other, was (it is hoped correctly) explained. 
It is therefore no matter for surprise if, in face of the diminution 
of one of the two factors of this momentum, viz. the mass, photo- 
lytic phenomena should be in abeyance. It might perhaps be 
safe to go further than this and maintain that the protoplasm is 
incapable of moving the grains because, whether from the ex- 
haustive calls upon it in connection with the thickening of a 
wall or walls, from the injurious effects (frequently observed) of 
continued sunlight or other causes, its capacity for movement has 
been diminished or lost. Iam also inclined to believe, a8 20 
other alternative suggests itself, that in those epidermal cells 
well provided with apparently healthy chlorophyll without starchy 
contents, the deficient factor is protoplasmic energy ; and if this 
be correct, the failure of photolysis to come off in epidermal 
tissues is easily understood. At any rate, it is submitted that, 
in view of its inability to stand the crucial test here applied to 
it, the “ activity" doctrine should henceforth be dismissed from 
Vegetable Physiology. 
Light and the Chlorophyll Plate of Mesocarpus. 
Stahl* is our creditor in respect of some beautiful discoveries 
of the movement of the chlorophyll plate of Mesocarpus scalaris, 
Hass. His observations may thus be summarized :— 
* Bot. Zeitung, 1880, p. 209, &e. 
