350 
On Purples or Ear-Cockle in Wheat. 
nature of the gall proves that the organs altered by the worm 
could not be the single central pistil, but a pair of opposed 
appendages. The only parts of the flower which could be con- 
verted into such galls are the two membranous scales forming 
the perianth of the flower. Accepting this interpretation of 
their nature, we find that the ridge in the gall would represent 
the margin of the leaf, while the fine hairs which cover the apex 
of the scale on its outer surface are converted into the short 
bristly hairs on the gall. I have never been able to detect any 
trace of stamens or pistils within the glumes, or scales contain- 
ing the galls. Davaine has observed, but only very rarely, 
organs which he recognised as a stamen or a pistil along with 
the gall. From his figures of these abnormal galls it is evident 
that the vibrio had attacked only one of the flower-scales, and 
that there still remained sufficient vigour in the axis to produce 
the imperfectly formed stamen or pistil. In the first stages of 
development the flowers of wheat are mere swellings on the 
simple axis or stalk. Each swelling lengthens, and becomes 
a lateral axis or stem ; and on this secondary stem swellings 
appear, which gradually enlarge, and shape themselves into 
the different parts of which the flower is composed. 
The vibrio must attack the flower at that stage in its develop- 
ment when the only swellings on the flower-axis are the lower 
and outer ones, which develop into the membranous scales of 
the perfect flower. 
Fig. 3. — Section of the Wall of the Gall, showing the great number 
of thick-walled Cells. 
When the vibrio penetrates the minute swellings a vigorous 
flow of sap is directed to the locality, as in the case of other 
galls, probably with the view of healing the injury. An 
abnormal development at once proceeds, which arrests the 
formation of the swellings which would become the stamens and 
pistil. The cells forming the two surfaces of the scale increase 
in number, and their walls become thick (Fig. 3), and form a 
dense protective covering to the enclosed worms. 
This interpretation of the nature of the organs altered in the 
gall, derived from the examination of a large series of galls, 
