COMPOUND ORGANS OF PLANTS. 



compound pistil, the ventral sutures are all united in the centre 

 of the fruit, and we see on the exterior only the dorsal sutures. 

 From this union of the carpels among themselves it follows, 

 that new lines will be formed at their points of contact. These 

 new lines called parietal sutures, are ordinarily seen on the 

 exterior of the compound ovary between the dorsal sutures, 

 and indicate the points where the walls of the several carpel- 

 lary leaves are joined. Finally, when the carpellary leaves, 

 instead of folding on themselves, uniting by their free margins 

 and soldering by their lateral surfaces, so as to cause their 

 ventral sutures to meet in the centre of the pericarp, and each 

 folded carpellary leaf to form a distinct cell in its cavity; unite 

 together by their margins, making only a slight introflexion 

 towards the axis of the pericarp, in such a manner as to form 

 a unilocular pericarp; the lines which result from this union 

 are called marginal sutures. The nature and origin of these 

 different sutures being understood by the student, he will find 

 no difficulty in comprehending the several varieties of valvular 

 dehiscence. 



Dehiscence usually takes place in simple fruits either by the 

 ventral or dorsal suture, or by both. Dehiscence takes place 

 by the ventral suture in the poeony and Wild Columbine 

 (Aquilegia) ; by the dorsal suture in the Magnolia ; and by 

 both sutures in the pea and Acacia. 



When the fruit consists of several united carpels or is com- 

 pound, the dehiscence may take place through the parietal 

 sutures so as to resolve the fruit into its original carpels, as in 

 the Colchicum, (Fig. 96,) when it is septicidal (septum a wall, 

 and ccedo I cut). This happens when the lamina of the car- 

 pellary leaves are only slightly united. When, however, these 

 lamina are firmly soldered together dehiscence takes place by 



