34 ARIL OF PASSIFLORA. [BOOK i. 



elongated and curved down on the point of attachment so as 

 to rest on the umbilical cord a little above the hilum ; neither 

 the opening of the internal integument nor the point of the 

 nucleus are to be any longer seen ; the external integument 

 has covered both, in consequence of its rapid growth. At 

 the same time, however, a very remarkable development has 

 begun on the umbilical cord. At the narrow end of this 

 organ, around the point at which it joins the ovule, we find a 

 circular rim which on one side surrounds obliquely the base 

 of the raphe, and on the other is interposed between the 

 umbilical cord and the ovule. The edges of this ring soon 

 extend and form a sort of membranous sleeve, the free edge 

 of which expands around the hilum. The evolution of the 

 ovules of Passiflora triloba stops here, and I have not been 

 able to follow the subsequent developments because its 

 ovaries are constantly abortive in the hot-houses at Mont- 

 pellier. Other allied species will, however, suffice. After 

 fecundation each ovule grows rapidly; the membranous 

 sleeve expands more and more, and that part of its edge 

 between the umbilical cord and the ovule extends towards 

 the exostome, and covers the top of the young seed as with 

 a hood. The latter becomes longer by degrees, and at last 

 the ovule, now a seed, is completely concealed in a loose fleshy 

 sac, attached to the border of the hilum and having a large 

 opening next the chalaza. In short, the annular rim, the mem- 

 branous sleeve, the hood which covers the top of the ovule, and 

 the open sac at its end, which completely conceals the seed, are 

 all one and the same organ in different stages of development. 



From the above it appears that this organ is formed after 

 fecundation ; that it is an expansion of the umbilical cord ; 

 that it does not adhere to the seed except at the hilum ; and 

 lastly, that it is completely open at the point opposite its 

 insertion : in this case I do not hesitate, in accordance with 

 the usual terminology, to call the organ a true aril. 



If all these characters united do not in this case leave any 

 doubt as to the nature of this envelope, it is not so much 

 owing to their real value as to our having followed them in 

 all the stages of the development of the ovule. These 

 characters become dtfubtful and insufficient when we apply 



