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. TJie 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 morphological sense ; physiological, inasmuch as it secretes a saccharine fluid, and morphological, inasmuch as its cells are distinguished both by their structure and their contents from the cells of the neighbouring parts of the plant. The 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. 1st. 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. -Fremy 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-Biimicated by the author.
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