considered in Relation to the Phyllode Theory. 449 
characteristic of the petiole in the case of the foliage leaf of R. Ficaria 
(Fig- 7 )- 
The limb of the leaf of Anemarrhena is characterized by a single 
series of normally orientated bundles (Fig. r), among which, however, the 
midrib is not well defined. This, again, is distinctly a leaf-base character. 
A similar lack of obvious symmetry about a midrib is found, for instance, in 
the sheathing leaf-base of the Umbellifer, Foeniculum vulgare , Mill. (Fig. 5). 
That some leaves among the Monocotyledons should be reduced to 
leaf-bases alone, ceases to be surprising when we remember how strongly 
developed this region is apt to be in the leaves of this Class as compared 
with Dicotyledons. The existence of a tendency towards the preponder- 
ance of the leaf-base is suggested not only by the countless Monocotyledons 
which have conspicuously long leaf-sheaths (e. g. many Gramineae, and 
species of Allium , Veratrum , &c.) 3 but also by the numerous bulbs in which 
this region, largely developed and utilized for food storage, survives the 
death of the remainder of the leaf. Among Dicotyledons with well-marked 
leaf-sheaths, we can trace the actual process of reduction from normal leaves 
to scale leaves consisting of leaf-bases alone. The Umbelliferae furnish 
obvious, examples — examples that were, indeed, known to the ancients. 
One of the most famous manuscripts of Dioscorides — the Vienna Codex 
associated with the name of Juliana Anicia, which dates back to the sixth 
century A.D. — includes a beautiful drawing of an Umbellifer called 
‘ Sphondylion in which every gradation is represented between normal 
foliage leaves and leaves of a definitely Monocotyledonous facies, in which 
the leaf-base alone is developed. 
The leaf-base phyllodes among the Monocotyledons may be regarded 
as representing the ultimate term in that arrest of apical growth which 
Professor Bower, 1 in a recent memoir on ‘ leaf-architecture ’, has recognized 
as a significant factor in foliar evolution. He points out that this arrest 
may go so far that ‘ the effective region originates basally ’. In extreme 
cases — such as the protective scales of certain Osmundaceae, Cycadaceae, 
and Angiosperms — it may even ‘ involve the atrophy of the whole distal 
region ’. 
II. The Petiolar Phyllodes of Asphodelus and 
Eremurus (Asphodeloideae). 
The genera Asphodelus and Eremurus were briefly cited in my 1918 
paper as examples of phyllodic anatomy from among the Asphodeloideae- 
Asphodelineae ; I propose here to describe the leaf structure in these cases 
1 Bower, F. O. (1916). I regret that I did not know of this memoir in time*to cite it in my 
general paper on the ‘Phyllode Theory’ (Arber, A., 1918); though dealing primarily with the 
Ferns, it also includes a very suggestive discussion, on broad lines, of the leaf morphology of the 
higher plants. 
