108 BULLETIN JÂRD. BOT. BUITENZORQ, SÉRIE 111, VOL. V. LiVR. 2. 



The development of ihe leaf in the oil palm. 

 {Elaeis giiineensis, JACQ.) 



The palm leaf lias been an object of investigation for almost a century. 

 Since DE Candolle (■*) in 1827 up to the présent, a fairly large list of 

 titles has appeared on the subject and the concensus of opinion of the 

 varions investigators has been that in the formation of the segments of 

 the fan-palm leaf and in the formation of the leaflets of the pinnate leaf, 

 essentially the same process goes on, namely that the parts of the leaf 

 blade originate from an oiiginally iindivided leaf blade. Hovv the ultimate 

 act occurs resulted into split camps — adhérents of VON MOHL's {-'^) inter- 

 prétation and, in more modem times, the point of view advocated by 

 GOEBEL (^) adapted from HOFMEISTER ('^). The field has narrowed down 

 to those who believe with VON MOHL that segments in the palm leaf arise 

 as a resuit of the formation of slits in the respective halves on either side 

 of the rhachis and of those who believe with GOEBEL that in the palm leaf 

 the segments arise as a resuit of folding of the young leaf blade owing to 

 the limited space which it has for development. GOEBEL's point of view 

 has had prééminence and it is the conventional interprétation that one meets 

 in text books and in semi-popular scientific treatises. 



ïïistorical. 



The histo; .,|1 development of the idea of palm leaf formation has been 

 dealt with m^-^'-^^dW in the works of VON MOHL (^2), Naumann P), and 

 Deinega (*'), se we shall not enter into a fuU discussion of it hère. 



De Can' ■ LLE (^) observes that in young palm plants the leaves are 

 entire and th , ater they begin gradually to tear, beginning at the upper end. 

 This, he main ams, is a natural phenomenon — the cause of the phenomenon 

 or mechanism which détermines this rupture is difficult to assign. 



VON MOHL (") we feel justified in quoting more or less in détail 

 since he was really the first to give a fairly complète picture of palm leaf 

 development. 



The leaf arises as a blunt excrescence from the growing point. As 

 this excrescence begins to develop it lifts itself above the plane of the 

 growing point and there is a very early indication of differentation of parts 

 of the leaf. 



The development of a pinnate leaf from a simple leaf in the palm is 

 unique, DE CANDOLLE states, in his "Organographie", that division of the 

 palm leaf into piiuiae or into segments of the fan leaf occurs in a characteristic 

 fashion, namely through tearing. DE CANDOLLE evidently had made his 

 observations on somewhat older leaves. VON MOHL found that the séparation 

 of the leaflets occurred long before the ultimate unfolding of the leaf. He 

 observed that the leaflets are held together by a loose parenchyma which 



