184 Scientific Proceedings, Royal Dublin Society. 



EXPLANATION OF FIGURES. 



Plate VI. 

 Fig. 



1. Leaf-rolling "artificially" induced in healthy IIp-to-Date plant by removal 



of tubers and axillary shoots. Photographed on fifth day after treat- 

 ment. 



2. Untreated control plant corresponding to plant illustrated in fig. 1. The 



two were derived from the halves of a single tuber, and were photo- 

 graphed at same time and to same scale. 



3. "Artificially" rolled leaf from healthy plant, as illustrated in fig. 1. 



Photographed on seventeenth day after original treatment of plant. 



4. One of- the previously "artificially" rolled plants, showing normal foliage 



after tubers and axillary shoots had been allowed to develop. Note de- 

 veloiDment of foliage leaves on floral shoot. 



5. Leaf from previously "artificially" rolled healthy plant after disappearance 



of rolling. 



6. Leaflet from "artificially" rolled healthy plant (on right), and from 



normal control plant (on left), both having been kept for sixty-four 

 hours in dark room. The leaflet from the treated plant contains a great 

 excess of starch, and has cleared only very slightly at the tip. The 

 normal leaflet is free fi'om stai'ch. 



7. Another pair of leaflets, one from "artificially" rolled plant (on right) and 



the other from normal control plant (on left), showing further progress of 

 starch disappearance after a period of seven days in dark room. 



8. The resumption of normal starch translocation in previously "artificially" 



rolled foliage. Leaflet on right, from iji'eviously rolled plant, contains 

 slightly less starch than leaflet on left from normal control plant. Both 

 kept tfor twenty-nine hours in dark room. 



9. Leaflet on left taken from diseased plant which showed early stage of 



rolling, and was then darkened in field for twenty-one days. Note lai'ge 

 amount of starch still present, and ])rogression of clearing from base 

 upwards. Leaflet on right, from healthy plant of same variety which 

 was darkened in field for t\\enty-four liours, is alm.ost free from starch. 

 Variety, British Queen. 



10. Accumulation of starch in leaves accompanying injury to liase of stalk. 



Leaflet on left was taken from top of injured stalk, and shows excess of 

 starch. Leaflet on right from top of normal stalk of same plant. Both 

 forty-two hours in dark room. Variety, Barley Bounty. 



11. Plant "(of season 1922) diseased with leaf-roll, being one of five diseased 



plants which were the progeny of a caged healthy plant on which capsid 

 l)ugs (Calocoria hipunctcdus) taken from diseased plants had been placed 

 in 1921. 



12. Healthy control plant (of season 1922), corresponding to plant shown in 



fig. 11. This was one of four healthy plants which were the progeny of 

 a caged healthy plant from which insects were excluded in 1921. The 

 two original plants of 1921 were derived from the halves of one tuber. 

 Both plants photographed to same scale. Variety, British Queen. 



