THE FRUIT AND ITS ENVELOPES. 



91 



chyma of wliich is confounded with that of the 

 sarcocarp. In this case it is always easy to dis- 

 tinguish the beginning of the epicarp, as at its 

 upper part, at a variable distance from the point 

 of origin of the style and stigma, it presents a 

 more or less prominent rim, formed by the re- 

 mains of the limb of the caliTc, which disappeared 

 after fecundation. 



The sarcocarp or mesocarp, is the parenchy- 

 matous part, in which are found collected all the 

 vessels of the fruit. It is excessively developed 

 in fleshy fruits, such as peaches, apples, melons, 

 and pumpkins ; all the fleshy part of these fruits 

 is formed by the sarcocarp. 



The endocarp, or internal membrane of the 

 fruit, is that which lines its internal cavity. It 

 is almost always thin and membranous. Some- 

 times, however, it is thickened externally by a 

 greater or less portion of the sarcocarp. When 

 this part of the sarcocarp becomes hard and 

 bony, it envelopes the seed, and constitutes what 

 is called a nul, when there is only one seed in 

 the fruit, and micletis when there are several. 



When the pericarp is dry and thin, it might 

 at first be thought that there is no sarcocarp. 

 Were this tenn always to imply a thick,^ fleshy, 

 and succulent part, no doubt it would very fre- 

 quently be wanting ; but the peculiar and dis- 

 tinctive character of the sarcocarp consists in its 

 being the truly vascular body of the pericarp; 

 in other words, it is formed by the vessels which 

 nourish the whole fruit. Now, as the pericarp 

 always contains vessels, the sarcocarp is never 

 wanting, although it is sometimes very thin 

 when the fruit, having attained its full maturity, 

 has dried. But, if the pericarp be examined 

 with attention, there will be seen between the 

 epicarp and endocarp, ruptured vessels by which 

 they were connected, and which are the remains 

 of the sarcocarp; for, as that part is always full 

 of aqueous juices previous to the maturation of 

 the fruit, when the fluid which it contains has 

 evaporated, it seems at first sight to have entu-ely 

 disappeared. 



The internal cavity of the pericarp, or that 

 which contains the seeds, may be simple, in 

 which case the pericarp is said to be imiloculwr, 

 or one-celled; as in the white poppy. At other 

 times, there are several cells or partial cavities, 

 whence the terms bilocular, trilocular, quinqiieh- 

 cular, multilocular, applied to the pericarp, ac- 

 cording as it has two, three, five, or more, dis- 

 tinct cells. The cells of a pericarp are separated 

 from each other by vei-tical laminae, which take 

 the name oi partitions or dissepiments. All true 

 partitions are formed in the same manner. The 

 endocarp is prolonged into the interior of the 

 cavity of the pericarp, in the form of two lamel- 

 lar processes, placed back to back, and connected 

 usually by a very thin prolongation of the sar- 

 cocarp. This is the mode of formation of all the 



true partitions. Those which are differently 

 constructed must be considered as false. 



In certain partitions, it sometimes happens 

 that the parenchymatous part of the sarcocarp, 

 which unites the two laminse of the endocarp, 

 dries up, when the two laminae disunite and se- 

 parate to some distance, so as to present the ap- 

 pearance of an additional number of cells. But 

 these spaces may easUy be distinguished from 

 true cells, by observing that the two laminae of 

 the endocarp have one of their sides covered 

 with broken vessels. Besides their mode of 

 origin and formation, another distinctive charac- 

 ter of the true partitions is, that they always 

 alternate with the stigmas or their divisions. 

 Certain fruits, on the other hand, present false 

 partitions in their internal cavity. Such are 

 those of some cruciferae, many cucurbitaceae, the 

 poppy, &c. The false are distinguished from 

 the true partitions: 1st, By their not being 

 formed by a duplicature of the endocarp properly 

 so called ; and, 2dly, By their generally corre- 

 sponding to the stigmas or the divisions of the 

 stigma, instead of being alternate, as the true 

 partitions are. 



The partitions are further distinguished into 

 complete and incomplete. The first are those 

 which extend internally from the upper part of 

 the cavity of the pericarp to its base, without 

 any interruption. The incomplete partitions are 

 not continuous from the base to the summit, but 

 leave a communication between the two cells. 

 Strammonium, or thorn apple, presents an ex- 

 ample of both these kinds of partitions existing 

 together in the same fruit. If the fi'uit of that 

 plant be cut across, it presents four cells, and con- 

 sequently {out partitions ; but of these partitions 

 two only are complete, while the other two do not 

 reach the top of the internal cavity of the peri- 

 carp, but rising only to two-thirds of its height, 

 allow the two cells, which they separate below, 

 to communicate together at their upper part. 



To be able to know and name correctly the 

 different parts which compose the pericarp, and 

 to distinguish them from those which belong to 

 the seed, it is of the greatest importance to esta- 

 blish the precise limits between these two organs. 

 As every seed must receive its nourishment from 

 the pericarp, it necessarily follows that it must 

 communicate with it by some part of its surface. 

 This point of communication has been named 

 the hil/um or umbilicus by botanists. The hilmn 

 is to be considered as the precise limit between 

 the pericarp and the seed ; in other words, all 

 the parts which occur externally of and above 

 the hilum belong to the perica/rp, while all those 

 which are situated beneath the hilum, are to be 

 considered as forming part of the seed. 



The seeds are attached within the pericarp to 

 a peculiar fleshy body, varying in size and form, 

 to which the name of placenta or trophosperm \% 



