considered in Relation to the Phyllode Theory. 3 1 7 
4. Leaves of the Ixioideae and Phyllodes of Acacia . 
I showed in the genus Iris that the phyllodic leaves range from the 
vertical ensiform type to the curious ‘ radial angular, or ribbed forms of 
Iris reticidcita , &c. A corresponding range is characteristic of the Ixioideae. 
We find a series beginning with typical equitant leaves, such as those of 
Sparaxis (Fig. 40. p. 318), Antholyza (Fig. 49), and certain species of Gladiolus 
(Figs. 43 and 44), which can be closely paralleled with the phyllodes of such 
Acacias as A. uncinella , Benth. (Fig. 42), and A, neurophylla , W. V. Fitz. 
(Fig. 41). The pseudo-midrib 1 {p.m.r.), formed from the two main lateral 
veins, is a striking common character of these Irid and Acacia leaves. In 
addition to the ensiform species, we have also, in the genus Gladiolus itself, 
certain more aberrant forms which may be regarded as developments from 
the type. Gladiolus ornatus , Klatt, for instance (Fig. 45 B), has a. leaf in 
which the ensiform character is becoming modified, and which shows a close 
resemblance to the phyllode of Acacia incurva , Benth. (Fig. 46). Gladiohis 
tristis , L., is a still more remarkable example, which departs to an extreme 
degree from the usual equitant type ; the cruciform section of the limb 
(Fig. 48 j) does not at first sight suggest a leaf at all. Fig. 48 A shows 
a plant of Gladiolus tristis with a number of young shoots. These each bear 
a succession of scale leaves sc. 2 , sc. 3 ) followed by a foliage leaf (fd) 
indicated in black. The clue to the peculiarities of the leaf structure is to 
be found in a study of the transition from the basal sheathing region to the 
limb. Figs. 48 B-E show this transition in the case of the tallest foliage 
leaf (/./.) in Fig. 48 A. At the base the leaf forms a continuous sheath 
(Fig. 48 B), which is ridged and furrowed, the ridges coming opposite to 
the bundles. A little higher, the sheath becomes open, and the ridges 
associated with the midrib and main laterals begin to predominate; the 
subsidiary ridges (r. and r'.) have altogether vanished at the higher levels 
represented in Figs. 48 D and E, their place being taken by the grooves 
g. and^-'. At the same time the margins of the sheath have fused, and are 
represented by the fourth main ridge opposite the midrib. Figs. 48 F-J 
show a series of sections through another leaf, in which the loss of the 
subsidiary ridges r. and r' . can be followed somewhat more easily than in 
the preceding series, and in which the ultimate form of the limb (Fig. 48 J) 
. is also included. In connexion with each of the four main ridges a pair of 
lateral keels or wings (k. and k ' in Figs. 48 H-j) are developed ; these wings 
are supplied by small vascular strands. The outstanding feature of these 
series of sections through the leaves of Gladiolus tristis is that the structure 
of the basal region of the limb*(Figs. 48 D, E, and 1) at once suggests that 
we are dealing with a cylindrical petiolar phyllode, merely modified by 
four deep invaginations or grooves, associated with slight lateral wings ; 
1 1 Cote mediane’ of Chodat, R., and Balicka-Iwanovvbka, G. (1892). 
Y 
