THE PISTIL. 



IOI 



increases, the different members of the same group will 

 often be found to afford transitional characters that make 

 evident what otherwise would be uncertain. 



Observe and name all the forms of placentae seen upon 

 the charts. 



EXERCISE XLIV. 

 Modes of Dehiscence. 



To understand the modes of dehiscence pictured in 

 this exercise, you have only to prepare a three-celled com- 

 pound ovary, as directed in Ex. XLII, observing the place 

 of the dorsal and ventral sutures, the relations of the valves, 

 and that the partitions are double. 



REGULAR OR VALVULAR DEHISCENCE occurs when the 

 ovary separates into the regular pieces called valves. 



Dehiscence is SEPTICIDAL when the ovary splits 

 through the partitions, each dissepiment separating into 

 its two layers, one belonging to each carpel (Figs. 313, 

 314, and 315), 



Dehiscence is LOCULICIDAL when the splitting opens 

 into the cells by the dorsal suture, as seen in the dia- 



FIG. 313. 



FIG. 314. 



FIG. 315. 



gram 316 and in Fig. 317, which represents the ovary 

 of a violet, where the carpels flatten out as soon as they 

 are released from each other. 



