The Anatomy of Ginkgo biloba. 91 
It will be remembered that in describing the transverse sections 
it was pointed out that the tracheids of the “ horns ” were cut 
longitudinally. In the longitudinal sections these are of course cut 
transversely (Text-fig. 17, 15 ). It is easy to realise how, during the 
transition of the main bundle to the concentric state, the anomalous 
tissue encircles the newly-formed half of the main bundle. The 
/ 
Text-fig. 18. Photograph of model of vascular tissue in collar, model 
shows xylem only and is viewed from above and behind. “ Horns” of main 
bundle point away from, and anomalous tissue points towards observer; white 
lines show curve of tracheids. Area marked M. filled with metaxylem (which 
is not shown in the model), hence the union of “horns” can be seen at D ; 
the lighter area C is the cambium. Note on one side the oblique gutter G 
caused by union of cambium of the anomalous tissue with that of the main 
bundle. 
tracheids of the main bundle belonging to the “horns” are also cut 
transversely, and they are situated at the base and inner side of the 
gutters. The union of these tracheids, when the main bundle 
becomes concentric, is shown in Text-fig. 17, 16 . Here they are 
seen running from either side of the main bundle across it to the 
centre, and at right angles to its length. 
Conclusions. 
The occasional occurrence of an apical bud between the ovules^ 
and the general anatomy, force us to consider the peduncle as a 
shoot bearing two lateral stalked ovules. Each ovule is attached 
to the peduncle by a short pedicel,and at the point of union of pedicel 
and ovule we have the collar. It is however difficult to account for 
the inverted vascular tissue of the collar if we consider it as a 
reduced carpel, a view which has often been expressed. The 
pedicel seems to have a petiolar structure relative to the main 
shoot, for the single vascular bundle which traverses it has xylem 
