1 88 
Notices of Books, 
The reaction of the cell-contents, as a whole, depends upon the 
relative quantities of alkaline protoplasm and of acid cell-sap which 
are present. The alkaline reaction is most marked in young cells 
in which the protoplasm preponderates, the acid reaction in old cells 
in which the cell-sap is present in excess. 
The author then proceeds to ascertain the cause of the alkalinity 
of protoplasm. He has recourse to analyses of the ash, and, taking 
leaves as giving the most reliable data, he cites a number of analyses 
which prove that there is a close relation between the amount of 
proteid in the leaves and the amount of potash in their ash. This, 
he believes, to be the cause of the alkalinity of protoplasm; and, 
after discussing the various possible forms in which potash may 
be present, he comes to the conclusion that it exists in combination 
with proteid. 
The next point considered is the structure and the chemical 
composition of chloroplastids. After giving an account of the views 
of Schmitz, Frommann, Meyer, Schimper, Pringsheim, and others, 
as to the structure of these bodies, the author states his own con- 
clusion, which is this: that a chloroplastid consists of a ground- 
substance in which are imbedded a number of fibrillae lying closely 
side by side ; there is no definite membrane, but there is a peripheral 
plasma-membrane. 
The colouring-matter of the plastid is confined to the fibrillae, which 
are coloured green throughout ; but it is especially collected into 
small spherical vacuoles ( grana of Meyer). 
The fibrillar structure of the chloroplastid is not apparent under 
normal conditions, but it becomes evident when they are caused 
to swell up by treatment with water. The fibrillae then swell up 
somewhat and separate, the ground-substance being dissolved. Hence 
it appears that the fibrillae and the ground-substance consist of two 
distinct proteid substances; the former is termed by the author 
chloroplastin , the latter, meiaxin. 
A long series of observations is given describing the effect of 
solutions of various salts, of potash, and of acids, upon chloro- 
plastids. Although these are all of interest, yet it is only possible to 
refer to some of them. The action of potash on the colouring matter 
is worthy of special note. When treated with solution of potash, 
the green vacuoles disappear, and the whole chloroplastid becomes 
uniformly coloured of a yellowish green. The author considers, in 
