YamfolskY: Study of OU paLni. 109 



is fused with the edge of the leaf iiito a narrow strip; tliat it is in close 

 contact with the pubescence of the leaf and when the parenchymous strij) 

 and pubescence dry up and fall off, the leaflets are set free. VoN MoHL 

 made his observations upon Phoenix and Cocos flexuosa. hi the young 

 stages the leaves of the plants (up to 5 mm,) consist of a homogenous 

 tissue. The middle, which later gives rise to the pétiole, is fhicker and 

 the blade is comparatively thin at the edges. Later a flat furrow arises 

 between the thickened mid-rib and the leaf edge. In later stages this leaf 

 lamina shows closely packed, rather deep, horizontal furrows and the leaf 

 blade is yet undivided. Still later thèse horizontal furrows develop into slits 

 which in Cocos flexuosa run through to both surfaces so that they can be 

 seen on the dorsal and ventral sides. Subséquent stages show that a leaflet 

 develops between every two slits. A longitudinal or cross section shows 

 that the leaflets are folded in two. In Cocos the mid-ribs of the leaflets 

 are on the dorsal surface so that the ventral surface of the leaf has twice 

 the number of slits. The edge of the leaf into which the ends of the leaflets 

 fuse is in the form of a continuons cell tissue (the edge of the unsegmented 

 lamina). This tissue dries up as the leaf continues to develop and isthrown 

 off as brown threads thus releasing the leaflets. In Phoenix the conditions 

 are somewhat différent since the mid-ribs of the leaflets are on the ventral 

 surface and the tissue which holds the leaflets- together at the edges is 

 continued into rather a thick membrane t>n the upper surface of the leaf 

 so that the slits are visible upon the ventral surface only The leaf then 

 arises as a homogenous mass and the leaflets owe their ^ 'l to an actual 

 division of the leaf blade. This division does not begi. lom the edge 

 towards the mid-rib but is limited to the blade surface and does not touch 

 the edge and in Phoenix the dorsal surface remains undivided "^ he undivided 

 part of the leaf blade differs from a true pubescence in its ^Sde of origin 

 inasmuch as it is not an outgrowth of the upper surface but 'an actual part 

 of the original leaf tissue. In Phoenix (not in Cocos) vascular bundles 

 traverse this undivided part of the leaf blade. 



TRECUL (^^) observed in Chaniaerops hiimilis that the very young 

 leaf is envelopfed by a sort of pellicle. By removing this pellicle he found 

 underneath, both surfaces in the form of divided and parallel ridges. The 

 lobes on the sides are always shorter than the others but they gradually 

 attain the same length as the others. The author does not attempt to 

 explain the origin of the leaflets or segments. 



In speaking later of the pellicle the author says: "One can recognise 

 the présence of this envelope in very young leaves at the time when the 

 grooves between ridges duringgrowth in \Qng\\\ o\ Chaniaedorea niartiana, 

 for example, appear. The leaves appear to develop in a translucent gelati- 

 nous substance which gives rise to the pellicle. In Chamaedorea it seems 

 to persist on the surface of the leaf following its contours during formation — 

 constituting for the leaf an epidermis or kind of cuticle." 



