326 Hill.— On the Roots of Bignonia. 
the stem. I have been unable to verify this. Most of my 
preparations show a very regular structure, e. g. those of the 
stage indicated in Fig. 5 ? and only in one case have indi- 
cations of six phloem -wedges been seen. 
The roots of Bignonia Unguis have a further interest in 
the fact that, at intervals, they swell out into tuberous growths 
resembling those occurring in the roots of certain species of 
Asparagus ; they may attain a diameter of about 1 cm. and 
a length of about ii cm. 
In a transverse section it is seen that there are many points 
of similarity between the tuberous and the ordinary roots. 
For instance, there is a well-developed periderm, and in the 
cortex there are numerous masses of sclerenchymatous 
elements. In the tuberous roots, however, they are arranged 
more regularly in concentric rings, and the masses also grow 
smaller towards the periphery ; the sieve-tubes and com- 
panion-cells are well marked ; and finally there are well- 
marked protoxylem-groups. 
The chief points of dissimilarity between the tuberous and 
other parts of the root lie in the great development in the 
former of parenchyma in the cortex and, to a lesser extent, in 
the pith ; and also in the breaking up of the xylem into 
separate masses, often by a certain amount of dilatation 
parenchyma. 
There can be no question as to the structures described 
above belonging to the roots. In the first instance the 
material was carefully examined for any evidence of stem- 
nature in the shape of buds, &c., but without any success ; 
then again the tuberous growths on the root are characteristic 
of the genus, the externally placed protoxylem is typically 
that of the root, and finally no phloem was found opposite 
the groups of protoxylem. 
Bignonia venusta closely corresponds with Bigonia Unguis 
in the possession of sunken phloem in the roots. The first 
indications of the anomaly were found in roots of about 
•97 mm. in diameter : in other roots of about 1 mm. diameter 
the phloem-wedges were about six cells in depth, while in 
