310 



ORGANOGRAPHY. 



Fig. 669. 



Fig. GC9. Pyxis of the 

 Monkey-pot iLecy- 

 this oilaria), with 

 transverse dehis- 

 cence. 



In the Monkey-pot (Lecijthis) {Jig. 669), 

 the lower pait of the ovary is adherent to 

 the tul)e of the calyx, and the upper ])ortion 

 is free ; when dehiscence takes place, it does 

 so in a transverse manner and at the part 

 Avhere the upper free portion joins the lower 

 adherent one, so that it would appear as if 

 the adherence of the calyx had some effect 

 in this case in producing the transverse de- 

 hiscence. Such fruits are sometimes termed 

 opercuJate, a term which is also applied hy 

 some botanists to all forms of transverse de- 

 hiscence in which the upper portion of the 

 fruit or pericarp separates from the lower in 

 the form of a lid or operculum. 

 Mr., Hincks, in a paper published in vol. xvii. of the Annals of 

 Natural Hislory, thus accounts for the transverse dehiscence of 

 the fruit; he thinks "that it arises from the force of cohesion of 

 the parts of the circle, the absence of any of the causes favour- 

 able to dehiscence along the midrib of the carpellary leaf, and 

 the operation of some force pressing either from without or 

 from wdthin on one particular line encircling the fruit." 



Transverse dehiscence may also occur in fruits which are 

 formed by a single carpel, as well as in the com])ound fruits 

 mentioned above. Thus the legumes of 

 Fig. 670. Coronilla, Hedysarum {fig. 670), Ornilhopus, 



&c., separate when ripe into as many portions 

 as there are seeds. Tlie separation taking 

 place in these cases has been supposed to be 

 effected by a process called solubility. ]Mr. 

 Hincks thus explains it in the paper above 

 alluded to; he says " the intervals between 

 the seeds being sufficient to admit of the 

 sides of the frnit cohering (which is pro- 

 moted in particular instances by special 

 causes), the swelling of the seeds afterwards 

 stretches the parts over tlicm in a degree 

 which this coherence prevents from being 

 equally distributed, drags tlie tissue forcibly 

 from the junctures which are fixed points, 

 and thus there being a strain in each direc- 

 ^'■'iS''^: Jo'JL"/:.^ ti^" ^''^^'^ ^'^c middle line of the juncture, the 

 contraction of drying in tlic ripening of the 

 fruit effects the se])aration." 



Some botanists regard such legumes as 

 formed of folded pinnate carpellary leaves 

 analogous to the ordinary pinnate leaves of the same plants, 



species of Saintfoiii 

 {Hcffuxariivi) sepa- 

 rating trunsversely 

 into one - seeded 

 portions. 



