considered in Relation to the Phyllode Theory . 305 
&c., did not arise by congenital concrescence, but is best regarded as 
a petiolar phyllode, comparable with a vertical Acacia phyllode, from 
which it differs in possessing a sheathing base. I tried to show that this 
view is supported by a study of the external form and internal structure, 
by a comparison with other ‘ monofacial ’ types, especially those met with 
in the Iridaceae, and also by the facts of the ontogeny as described by 
Goebel and Trecul. Since that paper was written, I have examined the 
apical bud of an Iris with ensiform leaves, and I have found that by 
dissecting it under the simple microscope I could satisfy myself that the 
leaves, down to one which was less than 1 mm. in its greatest dimension, 
showed a solid upper region distinct from the sheathing base. Fig. 5 
represents a section from a microtome series passing longitudinally through 
a similar apical bud, in which the same distinction of solid terminal limb (/.) 
and sheathing base (sh.) can be recognized even in leaves whose youth is 
extreme. The ontogeny thus yields no evidence at all for congenital 
concrescence. The same is true of the seedling structure (Fig. 2), for the 
solid phyllodic character is already recognizable even in the first plumular 
leaves (Figs. 3 and 4). 
Figs. 1 -10 illustrate the general anatomy of various ensiform Iris 
leaves. In Iris P seudacorus , L. (Figs. 1 A and B), and I. spuria , L. (Fig. 8), 
the bundles on the two sides of the leaf are equal and opposite ; in 
/. Kaempferi , Sieb., which is conspicuously ribbed (Fig. 7), and /. Doug - 
lasiana , Herb. (Fig. 9), the bundles on either side are found to be unequal 
in size and somewhat irregularly disposed, while in an undetermined species 
from China (Fig. 6) the bundles alternate. I also include here a sketch of 
/. tenuifolia , Pall. (Fig. io), because it has been figured by Chodat and 
Balicka-Iwanowska 1 as lacking a median bundle, whereas I find it to be 
of the normal Iris type in this respect. 
The ensiform leaves of Moraea Robinsoniana , C. Moore et F. Muell., 
and M ’. Maclcai , Hort. (Iridoideae), are represented in Figs. 11 and 12. 
Figs. 13 A and B show the leaf structure in the Kaffir Lily, Schizostylis 
coccinea , Backh. et Harv. (Ixioideae), which is essentially similar to that of 
Iris Pseudacorus. 
In my previous paper 2 the phyllodes of Acacia neriifolia , A. Cunn., 
A. scirpifolia , Meissn., and A. Cyclops , A. Cunn., were figured and compared 
with the leaves of various Iridaceae ; a further study of Acacias has shown 
that this comparison is even more widely applicable than was then 
supposed. Fig. 14 illustrates the structure of the phyllode of Acacia 
pendida , A. Cunn., which may be compared with the ensiform leaves of the 
genus Iris , especially with I. Douglasiana (Fig. 9). Figs. 40-4, p. 318, 
demonstrate the relation of Sparaxis , and of two ensiform species of 
1 Chodat, R., and Balicka-Iwanowska, G. ( 1892 ), Fig. io, p. 258. 
2 Arber, A. ( 1918 ), Figs. 1 A and B, 2 a-d, p. 474, and Fig. 21, p. 483. 
