considered in Relation to the Phyliode Theory. 323 
p. 311), while — outside the Iridaceae — non-vascular keels are associated with 
the main bundles of the plicate leaf of Curcidigo (Fig. 55). 
A further stage in the complexity of the foliated leaf is reached in 
Cypella (Figs. 50 h-n), Herbertia ( Alophia J ) (Figs. 51, a-d), and Cipura 
(Fig. 53), all belonging to the Iridoideae. Here the keels (k., k\, &c.) are 
developed into conspicuous lamellae, supplied by a number of bundles, and 
usually standing out at right angles to the plane of symmetry of each 
of the main vascular strands. Cypella Herberti , Herb., is of special interest 
in connexion with the phyliode theory, because, just at the junction of 
sheath and limb, the outline of the transverse section is almost circular 
(Fig. 50 K). At this stage the leaf is not unlike that of Gladiolus tristis 
at a corresponding level (Fig. 48 D, p. 318). The study of the transition 
from sheath to limb thus removes any difficulty which might have been 
felt in visualizing the limbs of both these leaves as cylindrical petioles, 
which at the extreme base retain some approximation to a typical petiolar 
structure, but higher up become rapidly modified. The final form to which 
the limbs attain is markedly different in the two cases (cf. Fig. 50 N, and 
Fig. 48 j, p. 318). Their ultimate differences depend upon the fact that 
Gladiolus tristis has only four grooves, arranged as two symmetrical pairs, 
while each main bundle is associated with two lateral wings, whereas 
Cypella Herberti is less symmetrically modified — the grooves, which are 
more numerous, are placed alternately, and there is only a single wing in 
connexion with each main bundle. 
7. The Leaves of the Crocoideae. 
While the Iridoideae contains 35, and the Ixioideae 18 genera, the 
third tribe of the Iridaceae, the Crocoideae, includes only the four — 
Romulea , Crocus, Syringodea, and Gal axial 1 We may first consider the two 
larger genera, Romulea and Crocus. Of these Romulea has by far the more 
extensive distribution ; it is found in the Mediterranean region and also in 
Africa (including South Africa), while in the other direction it even extends 
into England — R. Columnae, Sebast. et Mauri, occurring near Dawlish. 
The genus Crocus , on the other hand, is not represented outside the 
Mediterranean region. The distribution thus indicates that Romulea is 
probably the older type, and certain structural features tend to support this 
view. For instance, the extreme reduction of the whole Crocus plant 3 and 
the length of the flower-tube may be regarded as characters in which the 
genus has progressed farther than Romulea on the path of specialization. 
The leaf of Romulea also diverges less from the average Irid type than does 
1 This case has been studied in detail by Lindman, C. A. M. (1899). 
2 Pax, M. (1888), and Baker, J. G. (1892). It is possible that Galaxia ought to be transferred 
to the Iridoideae ; see p. 328 . 
3 Church, A. H. (1908). 
