MacDouGaL: Some CoRRELATIONS OF LEAVES 507 
lar reactions are shown by the elder (Sambucus nigra).* Healso 
found that the stipules of Vicia Faba were increased in superficial 
extension two to six times beyond the normal by the excision of 
the laminae in an early stage of development, and a similar exag- 
geration in the stipules of Lathyrus Aphaca resulted from the ces- 
sation of elongation or extension of the shoots. This correlation 
is not present in all plants, however, and not even in all Papilion- 
aceae, since it was seen that the excision of the laminae of Phaseolus 
multifiorus had but little effect upon the size and structure of the 
laminae.+ 
The excision of the leaves of Aristolochia, in the course of the 
present experiments, did not cause any notable increase in size of 
the stipules as seen by general inspection, although no examina- 
tion of the internal structure was made. 
Kronfeld made a series of experimental tests of this matter in 
1886, and found that the stipules of Pyrethrum Indicum, Rosa 
semperflorens, Rubus fruticosus, R. Idaeus, Sida Napaca, Trifolium 
Jiliforme and Urtica urens were not sensibly increased in size by 
the destruction of the laminae. The destruction of the laminae of 
Pyrus Malus was followed by an increase of the superficial expan- 
sion of the stipules amounting to a hundred per cent. The exci- 
_sion of the laminae of Pisum sativum was followed by an increase 
of the size of the stipules amounting to from fifty to one hundred 
per cent., while the excision of the stipules alone seemed to have 
the effect of causing earlier flower-formation. { 
Stomata were found on both normal and abnormal stipules in 
Prunus in my own experiments. No examination of the number 
of stomata on the adjoining surfaces of the stem were made, but 
Braun has found that defoliation causes the formation of an in- 
creased number of these organs. § The enlargement of the stimu- 
lated stipules of Prunus had apparently not been accompanied by 
a multiplication of the epidermal cells, since these elements were 
both larger and wider in surface view than the normal. 
* Goebel. Organography of Plants, x: 210. 1900. : 
+ Goebel. ( Beitrage zur Morphologie und Physiologie des Blattes.) Bot. Zeitung, 
38 : 836-837. 1880. : 
t Kronfeld, M. Ueber die ‘+ Correlation des Wachstums.’’ Bot. Zeitung, 44 : 
846-849. 1886. a : 
- @Braun, K. Ueber Veranderungen im Gewebe entlaubter Stengel und Zweige. 
(Inaug, Diss.) Erlangen. 1899. 
