40 Sargant. — Theory of the Origin of Monocotyledons 
seedlings depends at present on the comparative study of the 
four central tribes within that family. The passage from two 
massive bundles to a reduced double bundle in the position 
of a midrib has been traced step by step within those tribes. 
From the double bundle of Allium to the single one of 
Zygadenus is an easy step, and if the ‘ midrib ’ of Zygadenus 
be of double origin, we can hardly, in the absence of further 
evidence, venture to assert that the midrib of Veratrum is 
single. 
Similar reasoning applies to other characters of the vascular 
symmetry. 
The observations which follow on the vascular system of 
seedlings belonging to other monocotyledonous families were 
made, as explained before (p. i), on material already 
collected, and were purposely extended over a wide field. 
They led in the end to the selection of the Liliaceae for more 
detailed study, and in the light of the results obtained from 
it these preliminary observations have acquired a new value. 
Many of the seedlings examined show a marked likeness 
in the form of their vascular skeleton to the seedlings of 
Liliaceous species. Such are the forms commonly found 
within the Amaryllidaceae and Iridaceae. Anthurium is 
a striking instance from the Aroideae. 
The Palmae and Scitamineae, on the other hand, present 
types of their own. There is no embryological evidence to 
show that these are genetically connected with any Liliaceous 
form. But we may fairly ask whether their vascular structure 
is consistent with the theory of a single member formed by 
the union of two similar cotyledons. 
Amaryllidaceae. 
Six species belonging to four genera have been examined 
from this family. 
Four species — Alstroemeria sp., Bravoa geminiflora. Agave 
spicata , and A. Rovelliana — follow Liliaceous types in the 
vascular structure of their seedlings. 
The seedlings of Dovyanthes Palmeri and D. excelsa are 
