52 FALSE ARIL OF GUTTIFERS. [BOOK i. 



The anatropal ovules of Clusia flava are, in an expanded 

 flower, remarkable for the existence of two membranous hoods, 

 placed one over the other, which seem to proceed from the 

 edges of the exostome, and extending round this opening, to 

 cover, without any adherence, nearly a quarter of the young 

 seed. These hoods have sinuated margins and are of unequal 

 length, the upper one only covering about one half of the 

 lower one, which is applied immediately to the proper envelope 

 of the ovule. Have these unequal productions the same 

 origin ? Can the lower one be an extension of the primine 

 beyond its exostome, and the upper and shorter one the rim 

 of the endostome expanded into a membrane? We should 

 answer in the affirmative to the latter question if we stopped 

 at external appearances ; but a mere section of the ovule made 

 through the micropyle and the raphe is sufficient to show that 

 both of these expansions proceed from the primine only, and 

 that the endostome, which is very narrow, is not even thickened 

 at its edges. We are thus obliged to admit, notwithstanding 

 the singularity of the fact, that the external envelope of the 

 ovule, though simple in the greatest part of its extent, is 

 unlined beyond the exostome into two unequal expansions ; 

 and if I may be permitted to compare a leaf of the ovule with 

 the less modified appendages composing the corolla, I should 

 find examples of a similar process of unlining in the petals of 

 Lychnis, Silene, and other Cloveworts, which have at the top 

 of their unguis elegantly fringed lamellae. 



Whether the curious organisation just described is peculiar 

 to Clusia, and to the single species which I have observed, or 

 not, I leave to be decided by those who can examine other 

 species of this genus, or of the natural order to which it 

 belongs. But I do not doubt that the arillary cupule observed 

 in Quapoya, Havetia, Kenggeria, &c., is a false aril caused 

 by the expansion of the exostome. 



It will no doubt be remembered that the latter attains its 

 largest size on the seeds of the large-leaved Spindletree. 

 The details which I gave concerning this plant at the begin- 

 ning of the present memoir, will enable me to dispense with 

 a long description of a similar structure, found in other 

 species of the same genus or of the same natural order. 



