436 



Tin: AMi:i,'lc.\.\ XATl h'AI.IST [Vol. XLI 



rose and calls them basipetal (p. 525). There are two serious 

 objections to grouping the rose leaf with that of the blackberry or 

 potentilla. Neither the terminal nor the basal leaflets of the rose 

 are ever lobed to produce new leaflets as in the blackberry; and 

 in the blackberry the stipules are not involved in leaflet production 

 as in the rose. If the term basipetal is to be retained for the 

 blackberry and potentilla type, the leaf formation in the rose may 

 be described as stipular. 



Embryonic Leaves .— The interpretation of series of leaves such 

 as those shown in Figures 1-3 depends upon the study of their em- 

 bryonic development, for they are mature leaves and can never add 

 to their lobes or leaflets. The number of these parts is determined 

 before the leaf expands. 



According to Eichler (loc. cit.) a leaf may begin in two ways. 

 In some cases, immediately below the tip of the axis, there arises 

 simultaneously in all its parts, a wall-like proliferation of cambial 

 tissue corresponding to the entire insertion of the future leaf to- 

 gether with its stipules, if it is to have any. In other cases, beneath 

 the growing tip of the axis a low papilla or conical proliferation 

 appears, which quickly spreads laterally so that more and more 

 of the circumference of the stem is involved in the leaf formation. 

 This spreading ends before the leaf begins to hv snbdivided nito 

 lobes. In one of these two ways the pn monl uil Iraj i> tonn.Ml, 

 from which (and never from tlx- stem) all i)arts of rlie matuiv leaf 

 develop. They are not pushed out from the stem. The pri- 

 mordial leaf forms from the stem; after that, all growth of the 

 leaf is onlv an elaboration of the primordial leaf. 



After its fornuition, the primordial leaf begins to difterentiate a. 

 stationary basal zone, whieii is concerned only with the formation 

 one which ]>roduces the petiole 

 ,vavs follows blade formation; 

 1 before the stalk l)egins. In 



