Primitive A ngio sperms. 179 
habit, and the cotyledon and first leaf alike have a single median bundle. 
The first leaf has two laterals in addition. 
If the second cotyledon of the ancestor had really been transformed 
into the first foliage leaf, we should expect to find some traces of cotyledo- 
nary anatomy within it in forms not obviously reduced. But, on the con- 
trary, the less reduced forms are those in which the anatomical contrast 
between cotyledon and first leaf is most conspicuous. 
A third hypothesis is that both cotyledons of the ancestor united to 
form the single cotyledon of Monocotyledons. This view arises naturally 
from the comparative study of Monocotyledonous seedlings, and has already 
been discussed from the anatomical standpoint. But it is supported also by 
general considerations. I have already published the scheme founded on 
this hypothesis (72, 73). It suggests that the fusion of cotyledons which 
gave rise to the early Monocotyledons was an adaptation to a geophilous habit. 
Two questions arise immediately out of that suggestion : 
1 . How could adaptation to a geophilous habit lead to fusion of the 
cotyledons ? 
2. Would it account for the peculiar stem-anatomy of Monocotyledons, 
and for some at least of the minor features which separate that class from 
Dicotyledons ? 
Before attempting to answer those questions, the characters of geophi- 
lous plants must be more fully considered. 
Geophilous plants orgeophytes are species which have their permanent 
axis underground. Their green organs are produced at the beginning of 
each growing season, and die down at the end of it. But this is a very wide 
definition. It would include all the forms known to gardeners as herbaceous 
perennials, besides the more specialized ‘ alpines ’ and ‘ bulbs \ 
The more specialized geophytes are natives to climates in which a short 
season of growth is followed by a long period in which the conditions are 
unfavourable to vegetation. Such are alpine and arctic situations, where the 
summer may not last three months, and the ground is buried in snow for at 
least nine ; or dry climates with periodic rains, as on the South African 
veldt, and in localities of the Mediterranean region. Geophytes form a 
large proportion of the flora in such climates. They are characterized by 
massive underground organs, which in the dead season represent the whole 
plant. At that epoch it consists of a squat axis, often much enlarged to 
serve as a storehouse for food, and of one or more buds, which will produce 
the aerial organs in the next season. Roots may or may not be present. 
Some geophytes (e. g. Massonia pustulata •) have permanent roots which last 
over the dead season. Others (as many Orchids) have tuberous roots for 
aerial food-storage in place of tuberous stems. But the rule is that roots, like 
shoots, last over one growing season only, and die down at the end of it. 
