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STRUCTURE OF TRUIT. 153 



and the seeds are Parietal ; we see this in Viola, 

 Helianthemum, Passiflora, Reseda, Argemone, the 

 Capparideae, &c. 



Lastly, if the retreating parts only bear the seeds at 

 their base, and as it is this portion which is extended 

 towards the centre, the seeds are found placed at the 

 centre of the base of the fruit, and then the two fol- 

 lowing cases may happen : — 



1st. Sometimes the partitions are prolonged towards 

 the centre as far as the top, and then, not bearing seeds, 

 they are usually thin and membranous ; in this case, the 

 fruit has still several cells with the seeds at the bottom 

 of each, as in some multilocular Caryophylleae. 



2d, Sometimes the upper part of the partitions appears 

 to be wanting at maturity, because the carpels, which, 

 at the period of fecundation, were of the same length 

 as the placenta, afterwards elongated so as to rupture 

 the upper part of the partitions, and, more or less, com- 

 pletely isolate the placenta. This appears to take place 

 in several Caryophylleae. In all these cases, the fruits 

 are said to be Unilocular, and the seeds attached to a 

 Central placenta, although in reality the fruit is 

 always formed of united carpels, the retreating parts of 

 which bear the placentae on the inner margins. 



We have above seen, that each carpellary placenta is 

 prolonged into a style, that the union of the two placen- 

 tary styles forms the carpellary one, and that the union 

 of the carpellary ones forms the style properly so called. 

 This organization never presents any difficulty when the 

 placentae occupy the whole length of the fruit ; thus, 

 whether the placentae reach the centre, whether they 

 stop half-way, or whether they hardly exceed the margin, 

 we know that they have a direct communication with 

 the style. But what takes place when the placenta is 

 central, and does not reach the apex of the fruit ? 



