120 



Elementary Botany 



noticing in how many places the ovules are arranged (fig. 

 227). 



In some few cases it is difficult or almost impossible to be 

 able to say definitely in an iHdividual plant how many carpels 

 are present. The ovary, as we have seen, may be either inferior 

 or superior. In the former case it is either inserted in the 

 fleshy end of the flower-stalk, known as the thalamus or receptacle, 

 so that the calyx springs from above it ; or the calyx tube is 

 adherent to the wall of the ovary, the free limb springing from 

 the top. We often find two lines running down the ovary from 

 apex to base. These are known as the sutures : the one to- 

 wards the centre of the flower is the ventral suture, whilst the 

 one turned towards the perianth is the dorsal suture. 



FjG. az8. —Diagrammatic sections of ovaries : p, the placenta, to which the seeds are 

 attached ; A^ monocarpellary unilocular ; B^ polycarpellary unilocular ; C, polycarpel- 

 lary falsely multilocular : D polycarpellary multilocular ; r, dorsal suture, or midrib ; 

 h, ventral suture, or margins of carpel. (After Prantl.) 



When the pistil is apocarpous, each ovary contains but one 

 cell, or is unilocular, although sometimes there are false par- 

 titions growing partially across the cell. 



In syncarpous ovaries there are often numerous cells 

 agreeing with the numbers of the carpels (fig. 228, d), when 

 the ovary is bi-, tri-, or mnlti-locular. In other cases there is 

 but one cell (fig. 228, b), the ovary being unilocular. Some- 

 times there are partial dissepiments formed by an infolding of 

 the edges of the carpels (fig. 228, c). In some few cases there 

 are actual divisions ; thus the ovary of the Labiatse and 

 Boraginacese is originally bilocular, but by a subsequent division 

 it becomes divided into four cells. The ovules are not, as a 

 rule, distributed indiscriminately over the surface of the ovary, 

 but are arranged on certain parts of the wall, each of which is 

 called a placenta, whilst the arrangement of the ovules is spoken 

 — -oLajijllacentation. 



