248 Bertha Rees : Leaves of Primus cerasus. 



The above facts led me to believe that the leaflet was not an 

 actual outgfrowth, but was due to an attempt on the part of the 

 plant to produce pinnately-lobed leaves. 



Pluskel has already recorded the fact that " the leaves of 

 Prunus cerasus sometimes, though seldom, show pinnately 

 divided or lobed laminae.'" 



In the present instance this view was supported by the fact 

 that the grow^ths appeared in between the veins, where the leaf 

 would begin to segment, also that the different stages in the de- 

 velopment could be traced on the various leaves. Thus in Fig. 

 1 at (a) the margin is only slightly split, and the edges recurved, 

 at (h) and {r) the continuation of the margin of the leaf can be 

 distinctly traced into the leaflet, while at (d) the main leaf has 

 completely fused again above the segmentation. 



The explanation jDrobably is, that during development the 

 leaves became slightly lobed, and while the margins were still 

 recurved a partial fusion took place at the points of contact- 

 betAveen adjacent lobes, or in some cases a complete fusion in 

 the laminae outside the recurved edges ; as a result the edges 

 remained free on the under surfaces of the leaves and formed 

 appareiLt leaflets. 



Such an explanation would account not only for the position of 

 parts and arrangement of bundles in the main leaf and append- 

 age, but also for the incomplete nature of the connection between 

 the two halves of the apparent leaflets. 



The foregoing investigation was carried out in the Botanical 

 Laboratory of the Melbourne University, and I desire to record 

 my indebtedness to Professor EAvart for his interest and assist- 

 ance. 



EXPLANATION OF PLATE X. 



Fig. \. — Ventral surface of leaf of Prunus cerasus, showing 



position of appendages. 

 Fig. 2. — Transverse section through leaf and appendage. 



' Kkferknck Letters. 

 a-d. — Partially to fuUy-dovelopcd appendages. 

 e.— Main leaf. 

 f. — Appendaae. 

 g. — Bundle turning into appendage. 



1 Oesterr. Rot, Wocheiibl. iv., 1S.'>4, p. 12.5. 



