324 Robinson and Walk den.—A Critical Study of Crown Gall. 
Fig. 10. Portion of a shoot of Chrysanthemum frutescens five weeks after the inoculation of the 
apex by a single transverse needle-prick. Six galls at the bases of leaves separated by one or more 
internodes are seen. The whole of the extension of the shoot above the lowest gall ( ( g. .) has taken 
place subsequent to inoculation. Natural size. 
Fig. 11. Portion of shoot of Chrysanthemum frutescens , showing primary gall (p.g.) with 
rough exterior produced on the stem by needle-prick inoculation. At s.g. is a smooth secondary gall 
on the petiole of the leaf. Natural size. 
PLATE VI. 
Fig. 12. Portion of shoot of Chrysanthemum frutescens inoculated by a single longitudinal 
needle-prick at apex. Large primary gall (p.g.) with rough exterior on stem ; smooth secondary 
galls ( s.g . 1, s.g. 2, and s.g. 3) extending along midrib of leaf. Natural size. 
Fig. 13. Portion of shoot of Chrysanthemum frutescens inoculated by single transverse needle- 
prick at apex. Large primary gall (J>.g.) on stem, and on deformed leaf above this an elongated 
secondary gall Natural size. 
Fig. 14. Radial longitudinal section of the smooth secondary gall (s.g. 2) in Fig. 12. The tissues 
on the adaxial side of the protoxylem (px.) are subdividing, especially in the immediate vicinity of 
this. No marked intrusive growth. x 15. 
Fig. 15. Transverse section of secondary gall (s.g.) on deformed leaf seen in Fig. 13. Tissues of 
midrib modified to give a radial structure. Bacterium tumefaciens was present in the protoxylem 
region at the centre of this modified midrib. x 15. 
Fig. 16. Portion of stem of AHcotiana affinis , showing small primary gall (p.g.) at the upper end, 
produced by inoculation of the cut surface; a linear series of smooth secondary galls is seen extend¬ 
ing for some distance below the inoculated surface. B. tumefaciens isolated from s.g. 1. About 
five weeks old. Natural size. 
Fig. 17. Transverse section of the stem in the region of the secondary gall (s.g. 2) seen in Fig. 16. 
Three incipient secondary galls (s.g. 1, s.g. 2, s.g. 3) and also a tumour strand (t.s.) are seen in the 
cortex. At r. a root-rudiment is visible, x 12. 
Fig. 18. Portion of the xylem and pith of the section seen in Fig. 17. At px. the protoxylem 
elements are filled with bacteria, and the surrounding cells have begun to subdivide to give rise to a 
small tumour-strand, x 65. 
Fig. 19. Transverse section of similarly inoculated shoot of AHcotiana affinis to that seen 
in Figs. 16 and 17. Three tumour-strands are present in the pith, each having arisen around 
a centre of bacteria situated in intercellular spaces (i.s. 1, i.s. 2, i.s. 3). x 65. 
Fig. 20. Transverse section of similar tumour-strand to those shown in Fig. 19. B. tumefa - 
ciens present in the large intercellular space (i.s.) which forms the centre for the outward radia¬ 
tion of the disturbing influence leading to subdivision of cells, x 270. 
Fig. 21. Radial longitudinal section through part of inoculated stem of AHcotiana affinis 
similar to that shown in Fig. 16. The deeply-stained intercellular spaces (i.s.) containing bacteria are 
shown in the cortex with tumour-tissue arising by subdivision of cells on either side of the bacterial 
strand. The cut surface was situated a considerable distance above the portion figured, x 50. 
Fig. 22. Portion of the pith of Nicotiana ajfnis in longitudinal section. Zoogloea-like thread 
(z.) of B. tumefaciens advancing in the large intercellular space, x 550. 
Fig. 23. Portion of the marginal region of one of the incipient secondary galls seen in Fig. 1 7. 
At d tumour-cells appear to be intruding between the normal cortical cells, but at e the tumour-cells 
are seen to be arising by subdivision of cortical cells, x 150. 
