1922] ARBER—LEAVES OF FARINOSAE 89 
the Farinosae and those of two other cohorts, Helobieae and 
Liliiflorae; the Liliiflorae include those monocotyledons most 
nearly related to the Farinosae (11), while the Helobieae are 
somewhat more remote. 
The ribbon leaves of certain aquatic species of Eriocaulon 
recall the leaves of a corresponding form met with so frequently 
among the Helobieae (7), although, if my interpretation be correct, 
the ribbon leaves of Helobieae are of petiolar nature, while in 
those of Eriocaulon merely the leaf base is represented. Although 
the proportion of the parts is so different, it is-such a leaf as that 
of Restio tremulus (fig. 1 A), rather than that of a submerged 
Eriocaulon, which is equivalent to the ribbon leaf of, for instance, 
Cymodocea nodosa of the Potamogetonaceae (7). On the other 
hand, those leaves of the Farinosae in which the limb, although 
linear, is rather awl-like than ribbon-like, such as Tillandsia 
usneoides (Bromeliaceae, fig. 20), and Gaimardia australis (Centro- 
lepidaceae, fig. 5), may be closely compared with Cymodocea 
manatorum (7). The venation of the limb of Streptolirion volubile 
of the Commelinaceae again (fig. 9) resembles that of Alisma 
parnassifolium (7). A contrast with the Helobieae, however, is 
furnished by Monochoria hastaefolia (fig. 7), whose venation is 
essentially different from those of the species of Sagittaria, 
which it recalls in the outline of its pseudolamina (7). Turning to 
more detailed structure, the inverted bundles in the leaf limb of 
the Pontederiaceae and of Helmholizia find their analogue in those 
of certain Hydrocharitaceae. 
The occurrence of the ensiform leaf in the Farinosae, both 
in the Restionaceae, Xyridaceae, and Philydraceae, is another 
instance of the widespread distribution of this leaf type among the 
monocotyledons. It is known from the Helobieae, Spathiflorae, 
Liliiflorae, and Microspermae, as well as in the Farinosae. Not 
only in form, but also in internal structure, this type of leaf shows 
remarkable uniformity in the different groups. Xyris Wallichii 
(fig. 12.4) and X. brevifolia (fig. 18.A), with their alternating 
bundles, can be paralleled in Jris (1, 6). The fibrous margins, 
also, which are so marked a feature of the ensiform leaves of many 
Liliiflorae (6), reappear in Xyris. For comparison with the leaves 
