1845.] Linnean Society. 275 



disruption arises from the force of cohesion of the parts of the circle, 

 the absence of any of the causes favourable to dehiscence along the 

 midrib of the carpellary leaf, and the operation of some force press- 

 ing either from without or from within on one particular line encir- 

 cling the fruit ; and he proceeds to offer exj^lanations of those cases 

 with which he is most familiar. He takes lirst the circumscissile 

 capsule of Anagallis, in which he states that the central free recep- 

 tacle with the seeds upon it continuing to enlarge in both diameters 

 after the envelope has ceased to grow, and having occupied from the 

 first the entire cavity, it is naturally to be expected, since the chief 

 extension of the interior parts is upwards (the natural direction of 

 growth), while the enlargement of the seeds in the lower half tends 

 to press back the parts of the lower hemisphere, that uniform and 

 regular pressure will resolve a nearly spherical capsule into two 

 equal hemispheres. This remark he applies to Centunculus also, but 

 confesses himself at a loss to give any reason why the opening of 

 Trientalis, which depends on the same general causes, should be ir- 

 regular. For the separation of the lid of the capsule in Hyoscyamus 

 he accounts by the contraction and rigidity of the throat of the calyx 

 exercising a gradually increasing i)ressure around the upper part of 

 the capsule, and thus causing its separation by the first of the ge- 

 neral principles laid down. 



The author then proceeds to the case of Lecythis, which he thinks 

 is to be explained by the third of his general principles. In illus- 

 tration of this principle he refers to a monstrosity of the common 

 Tulij), described and exhibited by himself some years ago at a meet- 

 ing of the British Association. In this monstrosity, the upper leaf, 

 being unusually developed, has cohered by its edges so firmly as to 

 imprison the flower, and this constraint occurring at a period when 

 the stalk was increasing in length, and previous to any consider- 

 able enlargement of the flower-bud, the force applied was chiefly 

 vertical, and has carried off the upper part of the leaf in the form of 

 a calyptra, leaving the lower part in the shape of a cup, from the 

 centre of which the stem appears to rise. The separation of the lid 

 of the capsule of Lecythis he believes to be effected in an analogous 

 manner ; the septa which form the two or four cells into which the 

 fruit is divided meet in a thickened axis, and the outer part of the 

 fruit becoming (partly from its natural texture and partly from the 

 adherence of the torus and calyx) hard, solid and fully grown, while 

 the axis continues slowly to extend, and thus to press upwards that 

 portion of the capsule which rests upon it, causes that portion first 



