DoYLK — Some Researches in Experimental MorphologiJ. 407 



out under his supervision in the Botanical Gardens and Institute at Hamburg. 

 To his sage advice and direction as to the larger methods of the experiment 

 and the smaller but hardly less important details of technique — such as 

 grafting and culture and microscopy — is it due that the work has gone so far. 

 1 wish to put on record my heartfelt appreciation of his kindness to me. 



If we recall now the various experiments, we notice that the petiole has 

 been got to function as a stem in two ways. 



(«) A sprout lias been grafted on it, and the subsequent development of 

 that sprout has induced the changes in the petiole. 



(6) In the other eases — Begonia and Tovenia — we find adventitious buds 

 alreadj' growing on the leaf, almost inviting the attempt to root the leaf and 

 allow the adventitious bud to grow. 



At first sight then it would appear that method b should be chosen, but very 

 little consideration showed tiie advantages of the grafting method. Thus : — 



1. Leaving out of account the Pteridophytes, where the presence of buds 

 on leaves is comparatively common, we shall find that the number of plants at 

 our disposal is limited. Thus, Malaxis paliido^n , Drosera rotundifolia, Cardamine 

 pratensis (and many of its relations), Bryophyllmn calycinum, Tolmiea 

 Meitziesii, species of Lycopersioum, Pinellia tubevifera, many Begonias, 

 Torenia asiatica, Nymphaea Daubenyana would about exhaust the list — (4, 5, 

 7, 8). 



2. The captious critic can object to the use of any of these plants, on 

 the ground that they are abnormal plants. Their structure is exceedingly 

 plastic, and it could be argued that any response in the petiole to change or 

 increase of function is but a peculiarity of these, and could not be taken as 

 indicating anything of deep importance in plant structure. Of course, the 

 argument is speciousness itself. The more plastic the plant, the more it is 

 sought after by those interested in functional hyperplasies and kindred 

 phenomena. 



3. But there is a final argument which eventually settled the question, and 

 it is the difficulty of the proper culture of these adventitious buds. In most 

 cases the influence of correlation is very manifest. Thus, to note one — 

 Bryophijllum (Groebel, 9 and 10 ; Winkler, 5J. This is a well-knowu 

 plant belonging to the Orassulaceae. It has an ovate, somewhat dentate, leaf. 

 At the bases of the small bays at the edge of the leaf, there are nearly always 

 found small buds. As long as the leaf remains iu connexion with the mother 

 plant, so long do the buds remain dormant. If the apex of the mother plant, 

 as well as all the normal axillary buds, be removed, the adventitious buds on 

 the edges of the leaves develop. Not all of them do so. The largest do so at onoe ; 

 those that are beaten in the race remain still dormant. They may also be 



8 u 2 



