STRUCTURE.] FALSE DEHISCENCE. 7 



of Lecythis, the extent of the loose cover corresponds with 

 the extent of the axis, and what remains of the latter continues 

 attached to it. As regards Lomentaceous fruits in general, 

 the author believes that the intervals between the seeds being 

 sufficient to admit of the sides of the fruit cohering (which 

 is promoted in particular instances by special causes), the 

 swelling of the seeds afterwards stretches the parts over 

 them in a degree which this coherence prevents from being 

 equally distributed, drags the tissue forcibly from the junc- 

 tures which are fixed points, and thus there being a strain 

 in each direction from the middle line of the juncture the 

 contraction of drying in the ripening of the fruit effects the 

 separation." 



Valvular dehiscence, which is by far the most common 

 mode by which pericarps open, must not be confounded with 

 either rupturing or solubility, irregular and unusual con- 

 trivances of nature for facilitating the dispersion of seeds. In 

 valvular dehiscence the openings have a certain reference 

 to the cells, as has been already shown; but neither rup- 

 turing nor solubility bear any distinct relation to the 

 cells. Rupturing consists in a spontaneous contraction of 

 a portion of the pericarp, by which its texture is broken 

 through, and holes formed, as in Antirrhinum and Cam- 

 panula. Solubility arises from the presence of certain 

 transverse contractions of a one-celled pericarp, through 

 which it finally separates into several closed portions, as in 

 Ornithopus. 



For the nature of the placenta and umbilical cord see the 

 observations under ovary. Of these parts, which are mere 

 modifications of each other, the former often acquires a 

 spongy dilated substance, occasionally dividing the cells by 

 spurious dissepiments, and often giving to the fruit an 

 appearance much at variance with its true nature. 



In some seeds, as Euonymus europseus, it becomes exceed- 

 ingly dilated around each seed, forming an additional envelope, 

 called aril. The true character of this organ was unknown 

 till it was settled by Richard : before his time the term was 

 applied, not only in its true sense to an enlargement of the 



