48 OTHER FALSE ARILS. [BOOK i. 



extending from this point to the stigma. Other ovules, 

 however, instead of bringing their exostome near the peri- 

 carp or the placenta, apply it to their funicle, which in this 

 case either contains the conducting tissue or takes its place. 

 If there is any doubt as to the latter statement, it is only 

 necessary to recur to the ovules of Opuntia, which are, long 

 before impregnation, completely covered by a thick accessory 

 envelope, and the true micropyle of which, in no way cor- 

 responding with the orifice of the false testa called by us 

 false micropyle, can have no direct communication with the 

 exterior. It is clear that in this case the fecundating agent, 

 whatever it may be, pollen-tube or fovilla, cannot pass directly 

 from the pericarp to the ovule, since the latter is completely 

 covered by the accessory envelope before mentioned. And 

 since the ovule is in communication with the ovary only by the 

 funicle, the latter alone can transmit fecundating matter to it. 



Many genera of Indian Figs are so intimately allied to one 

 another, that great analogy might be expected to be found 

 between the integuments of their seeds. But such is not the 

 case ; the remarkable organisation of the seeds of Opuntia is 

 not found in Epiphyllum, Khipsalis, or Mammillaria, even 

 when their fruit is ripe. Cereus peruvianus, the ovary of 

 which I have only been able to observe sometime after flower- 

 ing, has no trace of any accessory envelope on its ovules, 

 although the funicles were at this time curved in the same 

 way with respect to the ovules, as those of Opuntia before 

 expanding into a membrane. 



If the anomalous production just described has only been 

 as yet found in a single genus of plants, such is not the case 

 with the expansions of the exostome, the type of which is 

 furnished by Euonymus. These, which are very common, 

 and the nature of which has often been mistaken, deserve 

 more especially the name of false arils, and coincide with 

 certain modifications of the testa, which it will, perhaps, be 

 useful to notice. 



The testa, it is well known, often contains in its thickness 

 very different layers of tissue. Sometimes its exterior is 

 crustaceous, and the vascular network it contains is hidden, 

 like the raphe, under one or more hard opaque plates. This 



