182 EVOLUTION OF PLANTS 
Angiosperms, but shall refer to this later. The effect 
of fertilization may extend beyond the fruit itself and 
involve the calyx, as in the apple or pear, or even the 
summit of the floral axis, as in the strawberry or fig. 
The embryo-sporophyte in different Angiosperms 
shows a very different degree of development at the 
time the seed ripens. Sometimes, especially in para- 
sitic plants, it consists merely of a small mass of cells 
without any external differentiation. On the other 
hand, as in the pea family, it finally occupies the whole 
cavity of the seed, and all the parts, stem, root, and 
cotyledons, and the terminal bud, are perfectly formed. 
The remarkable complexity shown by the fully devel- 
oped sporophyte of the Angiosperms offers a marked 
contrast to the extremely reduced gametophyte, and it 
is in this group that the development of the sporophyte 
reaches its most complete expression. From minute 
undifferentiated aquatics like the little duckweed 
(Lemna) (Fig. 45, D), every grade of development is 
encountered, up to trees rivalling the giants among the 
Conifers in point of size, and far surpassing them in the 
perfection of their parts, especially the flowers. 
In marked contrast to the Gymnosperms, which are 
restricted in their range, some forms of Angiosperms oc- 
cur under all conditions. Some are aquatics, even grow- 
ing in the ocean, while others are inhabitants of almost 
absolute deserts. Some are stately trees, while others 
are minute, almost microscopic, herbs living but a few 
weeks. Especially in the tropics, where the struggle 
for existence is keen, do we find Angiosperms taking 
advantage of every opportunity offered,— some lift 
themselves by tendrils or by twining their stems about 
