128 Bulletin Jard. Bot. Buitenzorg, Série III, Vol. V. Livr. 2. 



by most botaiiists as the explanation of the origin of leaflets. It serves as 

 the basis of GOEBEL's, Eichler's and Deineqa's work. It can readily be 

 seen tliat HOFMEISTER made his observations on late stages where ail the 

 critical steps had long since happened and that his material consisted of 

 already coinpleiely formed leaflets held to-gether by the enveloping tissue. 



The name of GOEBEL (") is always associated with the folding theory 

 of the origin of leaflets. We hâve already quoted him and shall do so 

 again for the sake of emphasis. "The parts of a leaf blade (palm) do not 

 resuit from branching of the leaf but arise from the division of the lamina 

 into definite segments following the death of the tissue holding thèse 



segments to-gether " If we examine the figures given as 



évidence of this phenomenon we find them unconvincing since there are 

 so few of them. His Figure 44, Cliainaerops /;zfl<:/'6'^a/'/j«, shows at a glance 

 that he had at his disposai stages that were much too old and misleading 

 when younger stages are lacking. Such stages are found in the young 

 plants of the oil palm where the lanceolate leaves still persist in a more 

 or less degree. Much earlier stages would hâve shown the unfolded character 

 of the leaf together with the présence of developing leaflets within the leaf 

 blade. GOEBEL's Figure 45 is as unconvincing as his other. His stage 1 

 of Figure 45 is not, in my opinion, a stage which shows folding but a 

 stage where the leaflets hâve pressed against the enveloping tissue giving 

 an appearance of folding and also resulting in a rupture of the tissue in 

 the form of slits between adjacent leaflets. His stage 3 of Figure 45, a 

 longitudinal section through the leaf blade, is too incomplète to lend much 

 significance to it, whereas number 2 of the same Figure 45 is in reality a 

 cross section of a leaf where the leaflets hâve oriented themselves obliquely 

 upwards perhaps like the stages shown in Figures 34, 35 and 36 Plate IV 

 of this paper. 



GOEBEL's évidence for the formation of a secondary "Haut" which 

 envelopes the folded lamina is entirely lacking and its origin is merely a 

 conjecture on his part. 



The évidence so far advanced for the theory of folding has been 

 conspicuously meager. The first extensive contribution accompanied with 

 figures was that of ElCHLER {^). We hâve already summarized his work. 

 Wheras the figures that he submits are extensive, he has failed in common 

 with those who hâve preceeded him to focus his attention on the stages 

 that yield the transition stages between the completely undifferentiated 

 lamina and the one that shows folds. Judged from the stages given in 

 his ** *** plates the argument for folding is amply supported. We find, however, 

 in ail his séries of stages given for the several forms, the intrafoliar origin 

 of the leaflets not only not indicated but even not suspected. The assumption 

 that between the individual leaflets definite tissue dies or dégénérâtes to 

 liberate them is in my opinion a gratuitous one based on inadéquate 

 observations on the origin of the leaflets, their growth, their orientation 



