308 Arber . — The Leaf Structure of the Iridaceae . 
(v) The association of ensiform leaf and winged axis in certain 
Monocotyledons and Acacias. 
A peculiarity which, in many cases among the Iridaceae, is associated 
with an equitant leaf, is the winging of the aerial axis in the plane of 
flattening of the leaf limb. In the herbarium of the British Museum 
(Nat. Hist.) I have observed this winging in the- following genera and 
species : — 
Aristea alata , Baker; A. anceps , Eckl. ; A. cladocarpa , Baker; A. com - 
press a , Buching. 
Bobartia gladiata, Ker-Gawl. 
Lapeyrousia abyssinica, Baker; L. compressa , Pourr. 
Marica caerulea , Ker-Gawl. ; M. gracilis , Herb. ; M. N or thiana, Ker- 
Gawl. 
Sisyrinchium acre , H. Mann ; .S'. alatum , Hook. ; 5 . angustifolium , Mill. 
(Figs. 25 C and E) ; .S'. arizonicum , Roth ; .S'. bogotense , H. B. et 
K. ; 5 . calif ornicum, Dryand. ; 5 . chilense , Hook. ; .S'. convolution, 
Nocca (Fig. 25 b) ; .S'. distantiflorion , Kranzl ; .S'. grande , Baker ; 
5 . hirsutum , Baker ; incurvatum , Gardn. (Fig. 25 a) ; 5 . zW<A'- 
folium , H. B. et K. : K micranihum , Cav. ; 5 . palmifolium , L. ; 
.S'. restioides , Spreng. ; 5 . tinctorium , H. B. et K. (Fig. 25 d) ; 
.S'. v agination, Spreng. 
When the winging is examined in detail, it is found that the leaf-base 
is continued downwards on either side of the true axis, from which it often 
remains conspicuously distinct (e. g. Sisyrinchium incurvation , Gardn., 
Fig. 25 a). This winging is chiefly to be observed in inflorescence axes, 
since these are frequently the only aerial stems produced by the plants of 
this family. In such cases it is the spathe below the inflorescence which 
is continued downwards to form the wing (e. g. Sisyrinchium tinctorium, 
H. B. et K., Fig. 25 D). The sharp distinction between the cylindrical 
axial region (ax.) and the flattened foliar region (/.) is very noticeable in 
the anatomy, e. g. Sisyrinchhon angustifolium , Mill., Figs. 25 C and E. 
The almost equal development of the wings on the two sides of the axis 
in this case, is due to the fact that the spathe forms a closed sheath round 
the inflorescence for some little distance above its attachment, and its 
downward continuation is thus capable of forming a wing both on the 
midrib side and on the side of the fused margins. This case may be 
contrasted with that of Acorus Calamus , L. (Aroideae), Fig. 2 6 a, in which 
the spathe is not sheathing, but is connected at the base of the spadix 
by a very narrow region of attachment. As a result, its downward 
prolongation produces a wing, but only on the side corresponding to the 
midrib, m.r. (Fig. 26 b). 
