THE FKUIT. 



81 



460. PLACENTATION is the manner in which the 

 ovules are arranged in the ovary. In the diagram, fig. 1 , 

 is seen the normal or typical placentation, with the 

 dissepiments reaching quite to the centre, and bearing 

 the placentae on their extremities, which are the two 

 confluent edges of the infolded leaf, and the ovules look- 

 ing directly to the floral axis. This form is called 

 AXILLARY PLACENTATION. 



461. But sometimes the whorl of carpellary leaves 

 apparently cohere only by their edges, without any in- 

 folding, or the walls may have become obliterated entirely 

 or partially, in the distention of growth. In fig. 2, the 

 dissepiments are partially obliterated; the ovaries are 

 seen occupying their place at the termination of the 

 walls ; while the ovary becomes one-celled by the abor- 

 tion or malformation. At fig. 4, the dissepiments 

 are completely obliterated, while the ovules appear at- 

 tached to their rudiments in the outer wall of the ovary. 

 These two last forms of placentation are called PARIETAL 

 (on the walls). 



462. By a complete reverse of the last position, the 

 ovules are thrown quite to the centre, while, at the same 

 time, the dissepiments being absent, they are left free. 

 This is called a FREE CENTRAL PLACENTATION, as in 

 fig. 3. Thus there are three modes of deposition in the 

 ovules Axillary, Parietal, and Free Central Placenta- 

 tion. The Primrose, fig. 6, is a fine instance of the lat- 

 ter mode. The round placenta, with its numerous ovules, 

 is attached only by a point at its base, and nearly fills 

 the ovary. Here only the dissepiments are wanting to 

 complete the normal structure, and it may be supposed 

 they are obliterated by the growth of the ovary. This 

 is certainly true in some cases ; for in the Pink and 

 Chickweed tribes, which are distinguished by a free cen- 

 tral placentation, rudiments of the walls may be seen at 

 an early stage of growth. Occasionally other forms of 

 placentation are met with, but the variations are unim- 

 portant. 



463. When the ovary consists of a single carpel, as 

 a matter of course, there can be no true dissepiments ; 

 but false dissepiments are occasionally to be met with, as 

 in the Flax. In determining the character of an ovary, 

 a careful distinction should be made between the really 

 simple organ, or that which is composed of a single car- 



Dcfine Placentation its normal form. How when the dissepiments are 

 partially, or wholly obliterated, and the ovaries on the walls how with ovaries 

 free in the centre? Define Parietal. How many modes of position in the 

 Ovules? Define each. What distinction necessary? Of what is a Simple 

 ovary composed a Compound ovary how distinguished when the dissepi- 

 ments are missing ? What shown in Meadow Saffron ? 



General subject. To what is the name applied botanically ? By this dofi- 

 11 



pellary leaf, and the compound ovary, which is a coalescent 

 circle of leaves. When the dissepiments are absent, the 

 number of carpels may be determined by the number of 

 placentae, if these are parietal, or by the number of styles 

 or stigmas, or by the grooves or sutures in the ovary 

 itself. In all parietal placentation, the ovary must be 

 one-celled. 



464. A fine illustration of the double nature of the 

 walls formed by the contiguous sides of the carpellary 

 whorl, is seen in the fruit of the Meadow Saffron, fig. 7, 

 where each of the three carpels is completely isolated, 

 and incloses its own ovules. 



CHAPTER XXIX. 



THE FPvUIT. 



465. THIS term signifies much more in botanical than 

 in common language, it being applied to the mature 

 ovary, and whatever organs it is coalescent with, as the 

 calyx in the Apple, and the receptacle in the Strawberry. 

 By this definition, the dry pod of the Cabbage is as truly 

 a fruit as the pulpy and delicious Peach. 



466. THE FRUIT consists of two parts the SEED, and 

 its ENVELOPE. The latter, taking its name from its office, 

 is called the PERICARP (around the fruit). With the 

 changes that occur in the growth and ripening of fruit, 

 the pericarp developes into two or more distinct and dif- 

 ferent portions, the exterior becoming firm or bony, and 

 the interior pulpy or fleshy, as in the Orange and Cocoa- 

 nut ; or the reverse occurs, and the outside is pulpy, and 

 the inside hard and bony, as in the Peach. When the 

 parts are thus distinct and separate, the outer portion is 

 called the EPICARP, and the inner portion the ENDOCARP. 

 But in such fruits as the Peach, the pulpy portion is 

 called the SARCOCARP ; and the hard shell, which corres- 

 ponds with the endocarp, the PUTAMEN. In the Cherry, 

 fig. 5, the outside integument, or skin, is the Epicarp, e ; 

 the pulp, s, is the Sarcocarp ; the bony shell of the nut, 

 en, is the stone, putamen, or Endocarp ; and g is the 

 seed. But often the pericarp remains of the same tex 

 ture throughout. In the acorn it is indurated ; in pods 

 membranaceous ; in berries, fleshy ; and in all such cases 

 no distinctions of parts are observed, but only those of 

 the outer and inner integuments. 



nition what are fruits ? Parts of the Fruit ? Name of the'En velopo ? Deflno 

 Changes in the Pericarp its parts. Define. Name of the pulpy portion in the 

 Peach the hard shell with what part correspond ? Describe tlic parts in tho 

 Cherry. Are these parts always to be distinguished ? How is Wic pericarp in 

 pods in berries? Wh&t is the opening of fruits called when fruits do not 

 open what called? 



