MacDougal : Some Corkklations of Leaves 511 



Laniiuin Orcala, Aconitinn Stocrkianutn, Clematis I Italba, Syringa 

 I'lilgaris, Corylus Avcllaiia titropnrpiircn, Gillcnia trifoliata, Pninus 

 Mahalib, Acsculus Ili/f/>ocastanmn, Ampclopsis hcdiracea, Aristo- 

 locliia Sip/io, Anr plataiioidcs, Rosa centifolia and Phascolns uiulti- 

 Jloriis* In addition to results previously cited, Braun concludes 

 also that the effect of delamination is to increase the photosyn- 

 thetic capacity of stems, retard the development of internodes and 

 interrupt the formation of woody tissue, all of which is confirmed 

 by my own results. Braun also suggests that the condition of 

 delaminated stems may be regarded as pathological, and that it is 

 directly due to mechanical interferences with the functions 

 involved. The condition of delaminated branches is undoubtedly 

 one of hypoplasia, but a careful consideration of the various fea- 

 tures involved leaves but little doubt that the failure to develop 

 is largely due to the absence of the customary stimuli in response 

 to which the several tissues carry on growth and differentiation in 

 a normal manner. The results in question are quite as much a 

 matter of correlation dependent upon stimulative factors, as the 

 variations in position and growth in compound leaves as discovered 

 by Zeleny. 



The more important facts observed as a result of cutting away 

 the laminae of the leaves of Acer and Pninits by severing the 

 petiole near the base may be briefly summarized as follows : 



I. The duration of the stipules of Pruniis is increased, so that 

 ten pairs of these organs are to be found on branches at a time 

 when only two or three pairs are present on a normal branch. 



II. The stipular surfaces exposed on delaminated branches of 

 Pntniis were sixteen times as great as on normal branches. 



III. The individual stipules of Pnimis were of a maximum 

 measurement in length and width on the delaminated branches and 

 were much larger than the stipules present on the corresponding 

 part of normal branches. 



IV. The position of the stipules of Prunus on delaminated 

 leaves was more divergent than the normal, and appro.ximated 

 that of a typical leaf. 



V. The structure of the stipules of Pruiins was modified in 



* Braun, .\. Ueber VerSnderungen im Gewebe entlaubter Stengel und Zweige. 

 (Inaug. Diss.) Erlangen. 1 899. 



