302 ORGANOGRAPHY. 



thin green layer, formed of mesocarp and epicarp. In the 

 Apple and Pear, the skin is the epicarp ; the fleshy part, Avhich 

 is eaten, the mesocarp or sarcocarp ; and the core containing 

 the seeds, the endocarp. A similar disposition of parts occurs in 

 the Medlar, except that here the core becomes of a stony nature. 

 In the Date, the outer brownish skin is the epicarp ; the thin 

 papery-like layer enclosing the seed is the endocarp ; and the 

 intermediate pulpy part is the mesocarp or sarcocarp. In the 

 Walnut, the woody shell enveloping the seed, which is com- 

 monly termed the nut, is the endocarp; and the green covering 

 of this, called the husk, consists of mesocarp and epicarp. In 

 the Orange, the outer separable rind is composed of mesocarp 

 and epicarp ; and the thin membranous partitions which divide 

 the pulp into separate portions form the endocarp; the edible 

 pulp itself, as already noticed, is a development of a^ucculent 

 parenchyma from the inner lining of the ovary, or probably 

 from the placentas only. In the above fruits, and numerous 

 others might be quoted, the different layers of the pericarp are 

 more or less evident, but in some cases, as in the Nut, &c., these 

 layers become so blended, that it is difficult, if not impossible, 

 to distinguish them. The examples of fruits thus mentioned 

 above, together with those previously alluded to, will show in a 

 striking manner, the very varying nature and origin of those 

 parts which are commonly eaten. 



Sutures. — In describing the structure of the simple carpel, 

 we found that it presented two sutures : one of which, called the 

 ventral suture, corresponded to the union of its margins, and 

 was consequently turned towards the axis or centre of the 

 flower; and another, termed the dorsal suture, corresponding 

 to the mid-rib of the carpellary leaf, and which was directed 

 towards the circumference. The simple fruit being formed, in 

 most cases, simply of the mature carpel, also presents two su- 

 tures, Avhich are distinguished by similar names. These, like 

 those of the carpel, may be frequently distinguished externally, 

 either by a more or less projecting line, or by a slight furrow ; 

 thus in the Peach {fig- 677), Cherry, Plum, Apricot, &c., the 

 ventral suture is very evident, although the dorsal suture has be- 

 come nearly effaced; while in the Bladder Senna {fig. 647), 

 Pea, and other fruits of the Leguminosoe, both dorsal and ventral 

 sutures are clearly visible externally. 



In a compound ovary with two or more cells, in which the 

 placentation is axile, it must be evident, of course, that the dor- 

 sal sutures can be alone observed externally, as the ventral 

 sutures of the component carpels are turned towards, and meet 

 in the axis of the flower, and are hence removed from view; the 

 number of dorsal sutures will also necessarily correspond to the 

 number of component carpels of which such an ovary is formed. 

 In a fruit presenting similar characters, we find of course a 



