Some Correlations of Leaves 



liv l)ANii:i. TKKMiii.v Mac1Jou(;al 



As a result of a long series o( experimental tests made in the 

 New York Botanical Garden, Mr. Charles Zeleny has found that 

 the excision of one of the leaOets of such plants as Trifoliimi pra- 

 tcusc (clover), Parthcnocissus quinqucfolia (Virginia creeper) and 

 Lupimis albiis (white lupine) resulted in alterations in the positions 

 of the remaining leaflets, alterations in tlic 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 tlic small 

 amount of evidence available would have led to the generalization 

 that the loss of an organ or a 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 b\' 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, f 



Goebel cites the fact that the stipels of the compound leaves 

 of Robuna Psaidacacia (locust) reach an abnormall}' 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. I He has also found that the destruction of 

 the vegetative points on such leaves as those of Bryop]iyllum is 



* Read before the Botanical Society of America, Pittsburg, July l, 1902. Now in 

 press in Bull. N. Y. Bot. Garden, vol. 3, no. 9. 



t Nemec, B. Ueber die Folgen einer Symmetriestorung bei zusammengesetzten 

 Blattern. Bull. Internal. Acad. Sci. Boheme. 1902. 



j Goebel. Organography of Plants, i : 210. 1900. 



503 



