152 Miscellaneous. 
Shell colourless, semitransparent ; when young, pale purplish. 
Inhab. China. N.W. Coast of Australia; Earl of Derby. Port 
Essington. 
The shells vary a little in the inequality of the hinge-ridges, but 
the hinder is always the longest. 
I may remark that Chemnitz gives the best character for the spe- 
cies, and has observed the character furnished by the hinge, which 
has been overlooked by Lamarck, and, as far as I am aware, by all 
recent authors. 
MISCELLANEOUS. 
The Effect of Iodine upon the Nectary. By Dr. R. Caspary*. 
WE consider the nectary as a peculiar organ, in a physiological 
as well as in a morphologieal sense ; physiological, inasmuch as it 
secretes a saccharine fluid, and morphological, inasmuch as its eells 
are distinguished both by their structure and their contents from the 
cells of the neighbouring parts of the plant. he cells of the nec- 
tary are very small, globular or nearly so, and they contain a pecu- 
liarly dense and granular matter. 
One of the most important inquiries connected with the physio- 
logy of the nectary is to ascertain, how the sugar which it secretes 
is produced ? 
This question is only, as we may consider, one special form of the 
general question, how is sugar produced ? 
Without entering minutely into the general inquiry, we will refer 
only to two modes of the production of sugar, which probably have 
a special bearing upon the case before us. 
lst. Sugar is produced from starch by the presence of diastase, 
which however cannot be prepared as an independent substance, and 
the existence of which is consequently disputed. Its active element 
appears to be nitrogen, so that we may say that sugar is produced 
from starch by the presence of a body containing nitrogen. 
2ndly. Sugar is produced from starch or cellulose by the presence 
of sulphuric acid. 
Frémy has made use of the latter mode of the production of sugar 
in accounting for the sugar in fruits. He endeavours to demon- 
strate that as starch or cellulose is converted into sugar by sulphuric 
acid, so certain substances, present in fruits and taking the place of 
starch or cellulose, are changed into sugar by the presence of free 
vegetable acids, which act in a similar way to sulphuric acid. This 
mode of the production of sugar has not yet been alluded to in ac- 
counting for the sugar of the nectaries of plants. 
The first mode of the production of sugar, according to which 
starch is changed into sugar by the action of a body containing ni- 
trogen, is employed by Liebig in his ‘ Chemistry of Agriculture and 
Physiology,’ in illustrating the formation of sugar in the trunks of 
trees, as in the maple. He however does not prosecute the subject 
* From the ‘ Botanische Zeitung,’ Feb. 23, 1849. Translated and com- 
municated by the author. 
