266 REPORTS ON THE SCATE OF SCIENCE. — ^1920. 



In May 1920 a draughtsman was engaged and trained, and some work was 

 put out at piece rates to another draughtsman , so that by the end of June the 

 cards completed numbered 1,649, while about 1,000 additional drawings etill 

 remained to be copied. 



Several Curators of Museums have kindly supplied the drawings of the 

 objects in their custody, and many more have undertaken to do this in the near 

 future, so that the work of the draughtsman will be mainly confined to filling 

 in the cards and visiting email museums and collections. 



On June 30 the expenditure amounted to 121. 5.?.. and the balance available 

 will pay for the drausrhtsman until the end of September. It is estimated that 

 about 200?. a year will be required to pay for the one drauerhteman resrularly 

 emploved, together with his travelling expenses, and the purchase of additional 

 material. 



Electromotive Phenomena in Plants. — Report of Committee (Dr. A. D. 

 Waller, Chairman; Mrs. Waller, Secretary; Dr. F. O'B. 

 Ellison, Prof. J. B. Farmer). 



During the last year we have taken a considerable number of observations on 

 the erowth of plants in the garden and of their amputated parts in the laboratory. 



We have examined into the relative physiological activity of growing and 

 non-growing zones as shown by their electrical response to electrical excitation 

 (blaze-currents).* The disposition of apparatus has been as described in 

 previous publications and is summarised in the diagrami overleaf. 



Observations have for the most part been carried out upon /m germantca 

 during the months of April, May, and June. The following is a representative 

 experiment : — 



Iris in its natural habitat in a flower bed with S.W. aspect. Leaf. 2.5 cm. 

 long, marked by Indian ink into 50 equal parts on April 24. The marked leaf 

 was examined from time to time and the markings remained apparently unaltered 

 in length, but raised en Tnonse with the growth of the leaf which was 

 measured and shown at the Rnyal Society on May 13 the lowest mark was 

 raised 5 cm. — i.e.. the growth had been exclusivelv basal. 



A similar leaf, about 20 cm. long, -was led off to the galvanometer from its 

 base close to the rhizome and from a point of the leaf 5 cm. hiorher up; it 

 exhibited a current of rest directed in the leaf from base towards apex. 



In response to a strong break induction shock. B to A. {i.e., ascendin^V 

 n, strongr blaze-current was amused in the same direction B to A (post-anodic 

 homodrome action current indicative of prpdominant rhange at B). A similar. 

 \mi less marked, response in the .same direction. B to A, was aroused by a strong 

 induction shock passed through the leaf from A to B (post-kathodic antidrome 

 response). 



f^trons- altematins; induction currents werp now passed through the A B 

 portion of the leaf for a period of one minute in order to effect its electrocution. 

 The blaze test bv a singrle induction shock first in the ascending then in the 

 descendincr direction failed to arouse anv marked resnonse : in pach case the only 

 visible effect was a small deflecMon antidrome to the exciting current — i.t.. in 

 the direction of nolarisation. The suppression of the blaze-current by electro- 

 cution can be definitive or temporarv. accordins; to strenq+h. 



ConchiHon. — I. The basal zone of the Iris leaf, in which alone active growth 

 is in progress, is electrically active (zincative) in relation to parts where active 

 growth has ceased. 



II. The zone of active growth is aroused to ereater physiological activity 

 (i.e., is more zincable) than are parts in which growth is not proceeding. 



' The rationale of 'blaze-currents' as a sign of life has been set forth in 

 several nrevious communications and is summarised in the following : Zertvrex 

 on the J^qns r>f TAff>. from- tJiPtr Electriml Aspect (.John Murray, London. 1903) ; 

 F/iygiolofjy the Servant of Medicine (University of London Press, 1910). 



