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 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- 

 municated by the author. 



