586 Horne: ANOMALOUS STRUCTURE ON LEAF OF BEAN 
long, and it could be traced back along the midrib as a white ridge 
to about 1 cm. from the base of the leaf. It was bent slightly away 
from the light and by the position of the leaf was directed downward. 
No root-cap could be seen. Trans-sections were made at vari- 
ORE 
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ye 
Oe; fs 
cS 
=S 
ce 
mm 
Pes 
FiGuRE 2. Transverse section of midrib, about 9 mm. from base, of the leaf 
bearing the anomolous appendage. 
ous points and stained with saffranin- Delafield’s haematoxylin. 
At about 7 mm. from the base of the leaf the structure of the mid- 
rib is normal, only a very slight ridge showing at its lower side. 
At 2 mm, farther the ridge is distinct with the narrow celled par- 
Se rr 
Bip 
FrGuRE 3. Longitudinal section of terminal portion of structure shown at 6 in 
figure 1. Xas 
enchyma about the bundle somewhat increased below the ridge 
but the fibrovascular elements not disturbed (FIGURE 2). At 8mm. 
farther the ridge has increased in size and a group of slightly nar- 
rower cells occupies nearly half of the space from the bundle to 
the epidermis. At 5 mm. farther the ridge is larger and the group 
of more slender cells is narrower and extends out towards its axis; 
the parenchyma is shrunken at one side. At g mm. farther the 
organ has reached its full size and commenced to separate from the 
midvein. An axial strand of slender cells is distinctly differentiated. 
here and entirely separated from the vascular bundle of the mid- 
Lig 
| Sota See eres 
