PHOGRESS OF MICROSCOPICAL SCIENCE. 
43 
number, and arrangement, are uniform in each species, but often quite 
different in the same genus, so that they may be used for critical 
specific characters ; and they are, moreover, connected invariably with 
the vernation of the leaf, and with the opening and closing (either by 
conduplication or convolution, according to the vernation of the 
species) which are so prompt in many grasses. That this movement 
takes place in virtue of the hygrometric expansion of these cells under 
moisture and their contraction in dryness, was made plain by the 
behaviour of sections of the leaf under the microscope, the closed 
conduplicate leaf of Sesleria opening instantly upon the application 
of a drop of water, when these cells in a band on each side of the 
midrib, before flattened or collapsed, became turgid and prominent. 
The leaves of Leersia orvyzoides are described as rolling up instantly 
upon being bruised or roughly handled, as if endowed with real 
irritability. We trust some of our young botanists will look to this, 
next summer. The split sheath of the leaves is one of the diagnostic 
characters of the Graminese. Exceptious in Glyceria, &c., were 
familiar. M. Duval- JoUve states that about a fifth part of the species 
have entire sheaths. Also that various grasses bear two, three, and 
even four leaves on one node ! " 
Microscopic Characters of Inflammation. — These have been admir- 
ably explained by Dr. Burdon Sanderson in his recent lectures on the 
subject. He said that it was in the batrachian eye the process may 
be most advantageously studied by touching the very centre of the 
corneal surface carefully with an extremely fine point of nitrate of 
silver. If the cornea so acted upon is prepared thirty-six hours 
afterwards with the aid of chloride of gold, it exhibits to the naked 
eye a central eschar surrounded by an area which can be distinguished 
from the rest by its somewhat brighter colour ; and if the tissue of 
this area is examined microscopically, it is found that within it the 
cornea corpuscles present an altered and, as it were, shrivelled 
appearance, so that the network of protoplasm, with the appearance 
of which everyone is familiar in the normal cornea, has lost its con- 
tinuity and integrity, while in the neighbourhood of their nuclei 
many of the corpuscles exhibit little holes, as if containing clear 
liquid, excavated in the protoplasm. From the presence of these 
holes — commonly spoken of as vacuoles — the zone may be called the 
zone of vacuolation. The appearances seem plainly to indicate that 
the caustic has, in the immediate neighbourhood of the eschar, injured 
or disintegrated the tissue by its direct action. What follows may be 
seen in preparations made some twenty-four or thirty-six hours later. 
By this time exudation has begun from the border of the cornea 
towards the injured part. By infection the vessels of the limbus have 
become congested, so that the conditions favourable for the sweating 
out of liquor sanguinis and the escape of leucocytes are present. 
Soon protoplasmic masses, differing entirely from those proper to the 
corneal tissue, present themselves among the normal elements, which, 
from the form they assume and their distribution, appear to be making 
their way centripetally. It is at this point that the question which it 
chiefly concerns us to answer presents itself. Ten years ago, if we 
