considered in Relation to the Phyllode Theory. 307 
concrescence. But the same line of evidence seems to me to indicate that 
the leaf of Iris is wholly different in its morphology from those of Phormium 
and Dianella , and that it does not, as Velenovsky assumes, represent a case 
in which the congenital concrescence of Phormium has been carried to an 
Figs. 15-23. Figs. 15-21, Phormium tenax, Forst. Fig. 15, two of the younger leaves 
of shoot C x e) 5 the left-hand leaf is open to the base, with no concrescent region ; the right-hand 
leaf has an open sheath at a, a concrescent region at b, and a flat limb at c. Fig. 16, youngest leaf 
of shoot in Fig. 15, open to base (slightly enlarged). Fig. 17, leaf 4 mm. high from another shoot, 
open to base (slightly reduced). Fig. 18, transverse section at a across sheathing region of right- 
hand leaf in Fig. 15 ( x 9, circa). Fig. 19, transverse section at b across concrescent region of right- 
hand leaf in Fig. 15 ( x 9, circa). Fig. 20, transverse section at c (incomplete) across limb region of 
right-hand leaf in Fig. 15 (x 9, circa). Fig. 21 A-c, seedling; Fig. 21 A, seedling (x |) / 1} istleaf; 
/ 2 , 2nd leaf; sk., sheath of cotyledon; si., stalk of cotyledon ; s., seed; Fig. 21 b , transverse section 
of l x in Fig. 21 A, at level x ( x 15, circa) ; Fig. 21c, transverse section of l x in Fig. 21 a at level Y 
(x 15, circa). Figs. 22 and 23, Dianella nemorosa , Lam. Fig. 22, leaf with sheathing region, a, 
concrescent region, b, and open limb, c (reduced). Fig. 23, transverse section of leaf in Fig. 22 at 
level b, where fusion is most complete (x 9, circa). 
extreme point. I look upon Phormium and Dianella as plants in which 
a partially ‘ pseudo-phyllodic , leaf structure and anatomy have been reached 
as a secondary modification. These two Liliaceous genera would thus be 
best treated at present as a case apart. It is possible that certain other 
£ monofacial ’ leaves among the Monocotyledons may also prove, on further 
study, to be comparable with those of Phormium and Dianella. 
