Some Correlations of Leaves 
By DANIEL TREMBLY MAcDOouGAL 
As a result of a long series of experimental tests made in the 
New York Botanical Garden, Mr. Charles Zeleny has found that 
the excision of one of the leaflets of such plants as 77ifolium pra- 
tense (clover), Parthenocissus quinguefolia (Virginia creeper) and 
Lupinus albus (white lupine) resulted in alterations in the positions 
of the remaining leaflets, alterations in the intervals between the 
remaining members and divergences from the normal size. 
Our knowledge of correlations at the present time would lead 
to the expectation that organs, the activity of which was comple- 
mentary or dependent upon a removed organ would show a de- 
creased or diminished development. On the other hand the small 
amount of evidence available would have led to the generalization 
that the loss of an organ ora part of an organ would stimulate the 
development of the remainder of the organ, or of the tissues carry- 
ing on the same function, in a supposed effort to bring the total 
functional performance up to the normal average. Mr. Zeleny’s 
results, however, demonstrate unequivocally that the excision of a 
leaflet in the above species is followed by a diminished development 
on the part of the remainder, which results in the accomplish- 
ment of a superficial extension, as represented by the length of the 
members, about seven per cent. less than the normal.* Results 
fairly in agreement with those of Mr. Zeleny have also been ob- 
tained by Nemec by less exact methods.+ 
Goebel cites the fact that the stipels of the compound leaves 
of Robinia Pseudacacia (locust) reach an abnormally large size 
when the leaflets are removed, which is an example of the induced 
enlargement of a structure in the effort to carry out the functions 
of lost tissue.t He has also found that the destruction of 
the vegetative points on such leaves as those of Bryophyllum is 
 *Read before the Botanical Society of America, Pittsburg, July 1, 1902. Now in 
press in Bull. N. Y. Bot. Garden, vol. 3, no. 9. 
Tt Nemet, B. Ueber die Folgen einer Symmetriestérung bei zusammengesetzten 
Bl&ttern. Bull. Internat. Acad. Sci. Bohéme. 1902. 
t Goebel. Organography of Plants, 1: 210. 1900. 
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