178 Sargant. — - The Reconstruction of a Race of 
underground axes of the former. That likeness is shared by the axes of 
geophilous Dicotyledons, for example many Umbellifers (Worsdell, 90), 
Podophyllum (Holm, 45). 
When Professor Henslow suggested that all living Angiosperms were 
derived from a common dicotylar stock, he stood almost alone in that 
belief. Of late years the tide has begun to turn. More than one botanist 
has come to the same conclusion on independent grounds. But though 
their conclusion is the same, these observers are not agreed either with 
Professor Henslow or with each other on the method by which descendants 
from the primitive dicotylar stock became Monocotyledonous. 
The latest contribution to the subject is that of Mr. A. W. Hill (39). 
Observations on an apparently monocotylar species of Peperomia , discovered 
by himself in a high Alpine situation on the Cordilleras, have led him to the 
conclusion that there are in fact two cotyledons present in the seedling. 
One is hypogeal and acts as a sucker ; the other has assumed the appear- 
ance and functions of the foliage leaf. The species is — as might be ex- 
pected from its habitat — very markedly geophilous in structure. Its 
seedlings seem to germinate in the spongy herbage of the locality. They 
are small, and their vascular tissue is so much reduced as to give them the 
appearance of aquatic seedlings, such as those of Alisma. 
Mr. Hill's interpretation of the structure of these seedlings may be 
correct, but it is always necessary to be cautious in dealing with the homo- 
logy of members much reduced from any cause. If, however, the seedlings 
of one species of a dicotyledonous genus have really become apparently 
monocotylar by the transformation of the second cotyledon into a foliage 
leaf, Mr. Hill has discovered a new method by which a dicotylar seedling 
may become monocotylar. He suggests that Monocotyledons may have 
been evolved in a similar way. 
The vascular structure of seedling Monocotyledons does not support 
this view. One of the most striking features in it is the distinct vascular 
symmetry of the cotyledon and the first leaf (72, pp. 38-40). The coty- 
ledon in the great majority of cases has no midrib. It is replaced either by 
a double bundle or by two single and quite distinct bundles. In the ex- 
ceptional cases the apparently single midrib often shows its double charac- 
ter during the transition ( Zygadanns ), or is allied to — and probably derived 
from — forms with the more usual dual structure ( Veratrum ). The first leaf, 
on the other hand, always has a midrib, and commonly one pair at least 
of lateral bundles. This structure is repeated in all subsequent leaves. 
Schlickum describes three species of Monocotyledons in which the coty- 
ledon closely resembles the first leaf. All three are aquatic plants : Tri- 
glochin Barretieri , T. maritimum , and Alisma Plantago (77, pp. 4-8). The 
vascular tissue is much reduced in all these plants owing to their aquatic 
