WIGHT ON THE FKUIT OF THE CUCU RBITACE^. 389 



tliree carpels, each of which is divided into two cells by its 

 placentiferous margin, being so introflexed as to reach the 

 dorsal suture. The sides of the carpel, and even sometimes 

 the introflexed portion, usually become extremely thick and 

 fleshy, forming the great mass of the ripe fruit, so that by 

 losing the general character of dissepiments, they might 

 almost be said to disappear, and thus at first sight a pcpo 

 would be said to be, and has been so described, a 1 -celled, 

 fleshy, indehiscent fruit, with parietal placentae that send out 

 sometimes false dissepiments towards the axis, as the cucum- 

 ber and gourd." 



This view, therefore, is essentially different from Dr Lind- 

 ley's; for, according to Arnott, the placentae are virtually 

 central, not parietal. The only difl'erence between a pepo 

 and an apple, being according to him, that the placentiferous 

 margins of the carpellary leaf are introflexed, and extend 

 outward nearly to the parietes of the fruit, in place of re- 

 maining in "the axis. Lindley, on the other hand, views a 

 pepo simply as a one-celled fruit with parietal placentae, the 

 cavity being occasionally divided into spurious cells by pro- 

 jections of the placentae. Neither is altogether consonant 

 with appearances, though that of Arnott appears the most 

 so ; but both, in common with all others that have yet been 

 promulgated, are incorrect both as to theory and fact. 



While our ideas of the structure of the most essential 

 organ of the plant, with reference to natural affinities, are 

 thus vague, can it be matter of surprise that we are unable to 

 trace its relations, and determine its affinities in the system of 

 plants ? 



What then is a peponida ? I have said above that it is 

 neither a one-celled fruit with parietal placentae, nor a three- 

 celled one with introflexed central placentae. But before I 

 can say what it is, and point out the difference between it 

 and a fruit of the usual construction, it is necessary to state 

 what the usual structure is. This I shall do by means of a 

 short extract from Lindley's Key to Structural Botany. 



354. "A Cari'El is formed by a folded leaf, the upper 



