RUDIMENTS OF BOTANY. XV 



placentas which occupy the edges of these dissepiments become what is 

 termed parietal. 



118. If the dissepiments are abortive or obliterated, the placentae remain- 

 ing unaltered in the axis, a free central placenta is formed. 



119. A one-celled ovary may also be formed out of several carpels in 

 consequence of the obliteration of the dissepiments ; as in the Nut. 



120. If the ovary adheres to the sides of the calyx it is called inferior, and 

 the calyx is said to be superior. 



121. If it contracts no adhesion with the sides of the calyx, it is called 



superior, and the calyx inferior. 



122. The ovule is a body borne by the placenta, and is the rudiment of 

 the future seed ; its position is of great importance in determining natural 

 affinities. 



123. When the ovule is fixed by its base to the bottom of one of the cells 

 of the ovary, of which it takes the direction, it is said to be erect ; or if it 

 hangs from the summit of the cell, it is inverted. 



124. When it is attached to the middle portion of the placenta, it may 

 have an upright direction, and is then called ascending, or point downwards, 

 and is then suspended. Generally, however, the erect and ascending ovule 

 are confounded under one name, and the inverted and suspended are known 

 by the term pendulous. 



125. The ovule is either sessile, or on a stalk called the funiculus or 

 podosperm ; and in either case the point by which the union is formed is 

 termed the base of the ovule, and the other extremity the apex. 



126. The ovule consists of a nucleus and two external coats ; the outer 

 coat is called the testa or primine sac ; and the inner, the internal membrane, 

 or secundine sac., or the legmen. 



127. The base of the nucleus is always incorporated with the base of the 

 internal membrane, and their common base is attached at some points to 

 the testa. The junction of the three forms the chalaza. 



128. The mouths of the primine and secundine sacs usually contract into 

 a small aperture called the foramen of the ovule, or the exostome. It is 

 through this foramen that the molecules of the pollen are introduced into 

 the nucleus ; and its position indicates the future position of the radicle of 

 the embryo, the radicle being always next the foramen. 



129. When the apex of the nucleus is contiguous to the base of the ovule, 

 a connection takes place between the base of the ovule and the base of the 

 nucleus, by a bundle of vessels called a raphe. ' , 



130. Fecundation having taken place, the floral envelopes usually fade 

 away, the stamens disappear and the pistil increases in size and becomes 

 the fruit. 



131. Hence the fruit should have the same structure as the pistil, but 

 this is not always the case, for as the pistil advances to maturity many al- 

 terations take place, in consequence of abortion, non-developmenf, obliter- 

 ation or even union of parts. 



