6 ANOMALOUS DEHISCENCE. [BOOK i. 



naturally to be expected, since the chief extension of the inte- 

 rior 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 Centun- 

 culus 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 irregular. For the separation of 

 the lid of the capsule in Hyoscyamus he accounts by the con- 

 traction and rigidity of the throat of the calyx exercising a 

 gradually increasing pressure around the upper part of the 

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

 general principles laid down. Lecythis, he thinks is to be 

 explained by the third of his general principles. In illustra- 

 tion he refers to a monstrosity of the common Tulip. In 

 this monstrosity, the upper leaf, being unusually developed, 

 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 considerable en- 

 largement of the flower-bud, the force applied was chiefly 

 vertical, and 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 appeared to rise. The 

 separation of the lid of the capsule of Lecythis, Mr Hincks 

 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 to become slightly prominent, 

 and finally by a strain upon the vessels of that particular 

 part to fall off in the shape of a lid. In Couroupita the pres- 

 sure is sufficient to mark the surface of the fruit with a promi- 

 nence, but from the partitions giving way early, and from the 

 abundant juices produced in the interior, there has not been 

 sufficient pressure to occasion disruption. In all the species 



