408 A TEXT-BOOK OF BOTANY. 



upon the number of carpels that make up the gynsecium ; as a 

 rule, there is a strong fibrovascular bundle which corresponds to 

 the mid-vein of each carpel. 



The PLACENTA is a development from the inner epidermis. It 

 is traversed by a fibrovascular bundle from which branches are 

 given off to the individual ovules ; it may have a conducting tissue 

 similar to that found in the style, and in some cases the epidermis 

 of the stalk of the ovule may be developed to a stigma-epithel. 



The OVULE not only possesses a distinct form as already given, 

 but the internal structure, by reason of the changes associated with 

 fertilization, is more or less characteristic for certain species and 

 genera. It has an epidermal layer, the outer walls of which are 

 more or less cutinized, and it consists for the most part of paren- 

 chyma cells rich in protoplasm and food-materials ; in addition the 

 embryo-sac contains a number of nuclei. The stalk and raphe are 

 connected with the placenta by means of a fibrovascular bundle. 



The NECTAR may be secreted by certain of the epidermal cells 

 of various parts of the flower ; these may resemble the ordinary 

 epidermal cells or they may be modified to papillae, as in the 

 spurred stamens of the violets, or to hair-like processes, as in 

 malva. The cells which secrete nectar constitute the ' nectar- 

 apparatus," and the walls are usually thin and more or less cutin- 

 ized. The nectar-apparatus is found more generally upon some 

 part of the stamen, but the sepals and petals are not infrequently 

 saccate or spurred, which adapts them for holding the nectar. 



V. OUTER MORPHOLOGY OF THE FRUIT. 



After the fertilization of the ovule or ovules, the parts of the 

 flower that play no further part either in protecting the seed or 

 aiding in its dispersal soon wither and are cast off ; in most flowers 

 the petals lose their color and, together with the stamens, style, 

 and stigma, wither and fall away shortly after fertilization. The 

 stigma may, however, persist, as in the poppy ; the style may like- 

 wise remain, as in Ranunculus, or even continue to grow or 

 lengthen, as in Taraxacum; in other cases the calyx persists, as 

 in orange and belladonna ; in still other cases the torus may be- 

 come fleshy and form a part of the fruit, as in pimenta and apple. 

 The fruit may consist, therefore, not only of the ripened pistil, 



