98 ALTERATION OF POSITION. 



very justly that no fair inference can be drawn from 

 these facts as to the normal placentation of Cruciferse. 



The same excellent observer has recorded the occur- 

 rence of free central placentation in malformed flowers 

 of Trifolium repens} 



In malformed flowers of Digitalis the change from 

 axile to parietal placentation may often be seen. Mr. 

 Berkeley describes an instance of this nature where the 

 placentas were strictly parietal, and therefore receded 

 from the distinctive characters of the order, and 

 approximated to those of Gesneracece. 



The same author alludes to certain changes in the 

 same flower where two open carpels " were soldered 

 together laterally, as was clear by the rudiments of 

 two styles, the placenta being produced only at the two 

 united edges, the outer margins remaining in the 

 normal condition. This may possibly tend to the ex- 

 planation of some cases of anomalous placentation, for 

 the only indication of the true nature of the placen- 

 tation is afforded by the two rudimentary styles, in the 

 absence of which the spongy receptacle of the seeds 

 must have been supposed to spring from the medial 

 nerve." 



In other cases the placentas were parietal above, but 

 axile at the base of the capsule, a striking instance of 

 the facility with which axile placentation becomes 

 parietal, the change being here effected by the pro- 

 longation of the axis, and the formation on it of a 

 second whorl of carpellary leaves. 



In double flowers of Primulacece similar alterations 

 in the placentation may often be observed. I have 

 seen in Primula sinensis sutural, parietal, axile, and 

 free central placentation all on the same plant; nay, 

 even in the same capsule the ovules may be attached 

 in various ways, and transitions from one form of placen- 

 tation to another are not infrequent. The late Pro- 

 fessor E. Forbes describes^ an instance of true foliar 



' ' Adansonia,' iv, p. 70. t. i. 



Henfrey's ' Bot. Gazette,' i, 265. 



