88 F. J. F. Shaw. 
orientation are seen to be scattered along the outer edge of the 
main bundle. 
Text-fig. 16, 3 , represents a section taken from the lower part 
of the collar. Here there are three anomalous bundles in addition 
to the main bundle. Moreover in one case the cambium of the 
main bundle has become continuous round its flank with that of the 
nearest inverted bundle. 
A little higher up, about the middle of the collar, the parenchyma 
on the other flank of the main bundle also becomes merismatic, and 
here likewise the cambium becomes continuous with that of the 
nearest inverted bundle. Text-fig. 16, 4 shows the vascular tissue 
slightly crescent-shaped, the xylem of the main bundle being on the 
concave side of the crescent and the xylem of the inverted tissue on 
the convex. The cambium of the main bundle is continuous with 
that of the inverted tissue round the “ horns ” of the crescent— 
these “horns” face towards the sterile ovule. At the back of the 
main bundle the inverted tissue consists of two small bundles. 
The crescent-shaped condition of the vascular tissue becomes 
more marked further up towards the ovule. The two “ horns ’ 
curve round and become much more prominent. So rapidly does 
this take place that the tracheids of the main bundle and of the 
inverted xylem at the “ horns ” run nearly horizontally through the 
parenchyma and are hence cut longitudinally in the transverse 
sections. The cambium remainscontinuous round the “horns” during 
this process (Text-fig. 16, 5 and 6 ). In Text-fig. 16, 7 , the cambium 
of the inverted tissue appears continuous right round the convex side 
of the crescent. The space between the two cambiums is filled with 
phloem, and it is difficult to draw a line of demarcation between the 
phloem of the inverted tissue and the normal phloem, but remnants 
of large parenchymatous cells can sometimes be discerned between 
the two. The tracheids of the inverted tissue are, on the whole, 
running outwards towards the periphery and are cut longitudinally 
right round the outer edge of the crescent. The parenchyma 
enclosed between the “horns” is intermingled with numerous 
tracheids and forms a sort of metaxylem. As regards the main 
bundle the tracheids of this metaxylem are centripetal. 
In the upper region of the collar, the inverted tissue continues 
to splay outwards and disappears from the transverse sections; it 
persists longest at the “ horns” (Text-fig. 16,8). The tracheids of the 
main bundle at each “ horn,” those on the inner side of the crescent, 
continue to run almost horizontally, and higher up in the collar they 
