ORGANS OF REPRODUCTION. 



Fiy. 598. 



remaining distinct, in which case the ovary is commonlj de- 

 scribed as lobed. In the Dianthus {fiy. 587) the ovaries are 

 completely united, while the styles are distinct ; while in the 

 Primrose {fiy. 567), the ovaries, styles, and stigmas are all 

 united. When two or more ovaries are thus completely united 

 so as to form one body, the organ thus resulting from their union 

 is called a compound ovary. 



When a number of carpels are thus completely united so as 

 to form a compound ovary, the compound body formed, may 

 either have as many cavities separated by partitions as there 

 are component carpels, or it may only have one. These ditfer- 

 ences have an important influence upon tiie attachment of the 

 ovules, as will be afterwards seen Avhen speaking of placcn- 

 tation. It will be necessary for us therefore, to explain at 

 once the causes which lead 

 to these differences. Thus 

 suppose we have three car- 

 pels placed side by side {fiy. 

 597, a); each of these pos- 

 sesses a single cavity, so that 

 if we were to make a trans- 

 verse section of the whole 

 {fiy. 597, b), we should neces- 

 sarily have three cavities, 

 each of Avhich would be sepa- 

 rated from those adjoining by 

 two walls, one being formed 

 by the side of its own carpel, 

 and the other by that of tlie 

 one next to it ; now, if these 

 three carpels, instead of being 

 distinct, were united by tlieir 

 ovaries {fiy. 598, a), so as to 

 form a compound ovary, the 

 latter must necessarily also 

 have as many cavities as 

 there are component carpels 

 {fiy. 598, b), and each cavity 

 would be separated from those 

 adjoining by a wall which is called a dissepiment or partition. 

 Each dissepiment must be also composed of the united sides of 

 the two adjoining carpels, and is consequently double, one half 

 being formed by one of the sides of its own carpel, the other by 

 that of the adjoining carpel. 



In the normal arrangement of the parts of the ovary, it 

 must necessarily happen, that the styles (when they are dis- 

 tinct) must alternate with the dis.sepiments, for as the former 

 are prolongations of the apices of the carpellary leaves, while 

 t3 



Fig. 507. a. Diagram of three carpels 

 placed side by side but not united. 

 b. A transverse section of the 



ovaries of tire same. Fig. .508. 



n. Diagram of tliree carpels unit- 

 ed by their ovaries, the styles be- 

 ing free. b. A transverse section of 

 the ovaries of the same. 



