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Sir J. C. Bose and Mr. S. C. Guha. 



It may be stated here that in petioles provided with four sub-petioles there 

 are four distinct bundles with four nerve trunks. But in specimens with 

 two sub-petioles we only find two bundles, corresponding to the two sub- 

 petioles. Two sub-petioles are found, generally speaking, in younger 

 specimens. The micro-photograph (fig. 6) shows one of the bundles. 



Experiment 3. — Electrical excitation in different layers : I shall now give 

 detailed results of localisation of the conducting tissue. The probe enters the 

 epidermis and is pushed in by steps of, say, 0'05 mm. ; it passes in succession 

 the cortex, C, the outer phloem, P, the xylem, X, the inner phloem, P', and 

 the central pith, 0. The thickness of the different layers is modified by age 

 of the specimen. In the records given below (fig. 7) the electric response 



Fig. 7. — Galvanonietric record of transmitted excitation in different layers of the petiole : 

 the first is the positive response of the epidermis, the second is the feeble negative 

 response of the cortex, the third, fourth, and the fifth are the enhanced responses in 

 the first phloem, the sixth shows absence of excitation in the xylem, the seventh is 

 the enhanced response in the second phloem, the eighth is the diminished response 

 in the pith. 



of the epidermis = +12 divisions of the galvanometer. I have shown else- 

 where (8) that the epidermis, which protoplasmically is more or less dead, gives 

 either a zero or a positive, in contradistinction to the normal negative response 

 of living tissues. The probe at a depth of 0*1 mm. encountered the cortex and 

 the response there was — 17 divisions. The phloem extended through - 15 mm., 

 the average depth being - 2 mm. The response in this region underwent a 

 sudden enhancement, as seen in the three responses —61, —65 and —40 

 divisions. The xylem which was at a depth of - 3 mm. showed no response, 



