4 SUPPLEMENT. 
coloration of these leaves, which are frequently called by the general 
name of perianth, the presence of nectar-glands, ets., are devices to 
attract insects and insure proper fertilization. 
The Spermatophyta are divided into the two following classes, the 
characters of each being appended: 
Cuass I. ANGIOSPERMAE. [Greek, signifying covered seeds. | © 
Plants having their ovules enclosed in a sac 
or ovary formed of one or more carpels. Fertil- 
ization effected by the growth of a tube from the 
pollen-grain after it has lodged on the apex of the 
ovary (stigma); this tube penetrates a small open- 
ing in the ovule, and through it the contents of 
the pollen-grain are transferred to the ovule. 
Cuass II. Gymnosprermar. ([Greek, sig- 
nifying naked seeds]; Plants having their ovules 
borne exposed on thesurface of a scale. Fertiliz- 
ation effected either by the growth of a pollen 
tube or by the direct contact with the ovule of 
small moving bodies known as antherozoids, anal- 
. ogous to the spermatozoids in animals; these are 
Fic. 2.—Branchiog stem 
of an Ephedra (amily discharged from the ripe pollen grain after it has 
Gnetacege) showing the flow- 
er clusters. lodged on the female sporophyll. 
sat Ainliyt - 
CHAPTER IL r ne doce viz 
The Class Gymnospermae. ' ! (Fig. 1.) Jae focte 
[ The Gymnosperms, as they are ee called, contain all of 
our familiar evergreen coniferous trees} ‘and therefore constitute a 
prominent feature of the forests in the colder temperate regions. The 
class is of great interest, not only by reason of its antiquity, but because 
it represents a vanishing type. Not more than 450 species of gymnos- 
permous plants are now known to exist, while in Cretaceous and 
Tertiary times the group was much greater. Certain genera like 
Sequoia, containing the redwoods and big trees of California, at present 
restricted to a small strip of territory on the Pacific coast, were 
formerly abundant in many different geological horizons of the country. 
The gymnosperms represent the lowest type of flowering plants, making 
a close approach in the details of their mode of fertilization and devel. 
