IN THE URTICACE^. 81 



to think that the corpuscles in question are analogous to the 

 deposits which, in time, obstruct the cavity of certain hairs, 

 in the Boraginece for instance ; and which, particularly in the 

 common Fig, may be seen prolonged into the cavity of the 

 bulb of the same kind of hairs. The cells in which the cor- 

 puscles arise would even, according to Schleiden, be urticating 

 hairs, whose base only was developed. The only argument 

 which it is necessary to oppose to this theory, is the fact that 

 the bodies in question are often seen beneath the epidermis 

 and even in the medulla itself. Moreover, the deposit con- 

 tained in the hairs of the Fig are formed in quite a different 

 way from the gummy, calcareous, pedunculate corpuscles of 

 Meyen, and behave towards reagents in a very different 

 manner. 



More recently, again, Payen's theory has found an anta- 

 gonist in H. Schacht, to whom we are indebted for a very 

 extended memoir on the subject. I shall content myself here 

 with remarking, that he adds absolutely nothing essential to 

 what Meyen had already stated with respect to the anatomical 

 constitution of these corpuscles. Schacht, moreover, adopts 

 entirely Payen's opinion as regards their chemical constitution, 

 and notices them besides as characterizing the tissue of another 

 large family of plants — the AcanthacecB — in which their pre- 

 sence would seem to have been first shown by M. Gottsche of 

 Altona. 



Lastly, I have myself for several years studied these sin- 

 gular corpuscles ; and the result of my observations has also 

 been completely in accord with that at which Meyen had 

 arrived. Struck with the differences, which seemed to me to 

 exist between these bodies developed in special cells, and all 

 the other mineral secretions of plants, I gave them the name 

 of cystolites {kxxttiq, Xidog). These concretions, moreover, 

 play a more important pan in the physiognomy of the plants 

 in which they occur than might at first be supposed, and are 

 capable of furnishing the most valuable diagnostic characters ; 

 it appeared a useful object, therefore, to describe them more 

 clearly than had hitherto been done. 



Their figure is most commonly spheroidal ; but in many of 

 the UrticacecB, and in a great number of the AcanthacecB, they 

 assume an oblong or moi'e or less linear form, attenuated 

 towards the ends, sometimes in that of a bow, or more rarely 

 of a horse-shoe shape. In the living plant they are visible 

 only on dissection or by transmitted light ; the leaves in which 

 they are contained then exhibit when viewed with a magnify- 

 ing glass, translucid lines or points, but from which it would 

 scarcely be possible to draw any precise diagnostic characters. 



VOL. IV. G 



