FROM SIMPLE LEAVES. 113 



prominent on their under surface, as in the Cast&r-oil plant, 

 by simple inspection of that under surface, we can easily trace 

 out the fibrous portion of each forming leaflet in the blade 

 of the leaf, and thus satisfactorily arrive at the same conclu- 

 sion, that the entire blade itself is a composition of partially 

 formed and organically united leaflets. Because the lateral 

 veins given off by the midrib of ^each forming leaflet may be 

 traced below the point where the division between the lobes 

 or blades of the leaflets ceases, and they become as it were 

 blended together ; for notwithstanding the confluence of the 

 fibre and parenchyma of the leaflets below this point, their 

 lateral veins still continue to be given off with the utmost 

 regularity, even down to their point of divergence at the apex 

 of the common petiole. The fibrous portion or framework 

 of the forming leaflets is therefore perceptible in the common 

 lamina or blade of the Castor-oil leaf; and it is not difficult 

 to imagine the form that the leaflet would assume when fully 

 developed and detached from its neighbor, as in the above 

 case of Rubus villosus. But the further development of the 

 leaflets of the Castor-oil leaf is arrested at this stage, and 

 therefore they are never found separate. 



The coalescence or union of leaves or leaflets with each 

 other in all instances results from a want of developmental 

 vigor in that fibrous portion of their lamina, which constitutes 

 their skeleton or framework ; hence, the most frequent cases 

 of union or coalescence, occur among the floral leaves where 

 the vegetative powers of the plant are gradually expiring. 

 Thus, when the sepals or leaves of the calyx, as also the petals 

 or leaves of the corolla, coalesce, we have produced what is 

 technically termed a monosepalous (or gamosepalous) calyx, 

 and a monopetalous (or gamopetalous) corolla, as in the Bell- 

 flower (Campanula Americana)] so, also, the metamorphosed 

 pollen-bearing leaves termed stamens, situated immediately 

 within the corolla, may unite with each other by their fila- 

 ments and become monadelphous, as in the Mallow and 

 Geranium, or by their anthers and become syngenesious, as 

 in the Dandelion ; or the filaments and anthers of all the 

 stamens may unite and form a single organ, a sort of vagina 

 15 



