548 LIFE-HISTORIES 
The Lycopodine, which comprise in a very few genera about 
600 species, occupy an intermediate place between Filicine and Equise- 
tine in the relative size of their leaves and in their arrangement which 
may be either alternate or whorled; but, while having the sac-leaves or 
sacs often in terminal cones, the sporangia are always solitary and 
never on the under side of a leaf; and there are no elaters. 
195. The pteridophyte division, fernworts (Pteridophyta) 
is made up of the three classes above named. Ferns being 
especially typical of them all, the plants of this division are 
conveniently designated as fernworts. 
While, as we have seen, mossworts were perhaps the first green 
plants out of water to succeed in standing upright, it is among 
fernworts that we first find vertical growth producing lofty trunks. 
Spores formed near the top of such a trunk are plainly given an 
immense advantage since they may be dispersed over an extensive 
area. This highly beneficial provision for the welfare of offspring 
was made possible by the development of roots able to absorb 
subterranean moisture, and of leaves that could utilize it in con- 
nection with the air and sunlight. A protective function with 
reference to the sporangia or to tender parts of the stem was easily 
assumed by these lateral appendages, and in some cases became 
their chief or only office, as happened with the sheathing whorls of 
Equisetum or the cone-scales of Selaginella. Various differentia- 
tions of the stem-parts, gave rise to more or less branched ascending 
axes, either independent or climbing, or to more or less horizontal, 
often subterranean stems in which the capacity for storing food was 
often especially developed, and from which vertical branches or 
vertical leaves arose during seasons favorable for growth. For the 
bearing of spore-sacs either leaf-parts or stem-parts were available; 
and sometimes the one, sometimes the other was used. Nurse- 
plants were depended upon to foster the embryo and prepare it for 
independent, vigorous life; and the nurse itself was so well provided 
with reserve food that it could afford to dispense with food-making 
organs of its own to a considerable extent. It is thus perhaps of 
evolutionary significance that the gametophyte of fernworts is 
commonly much simpler in form and of less vegetative importance 
in the life-history of the plant than is the case in mossworts. An 
extreme of specialization in the reproductive function of the game- 
tophyte is found in those fernworts which have male and female 
spores, the latter having in general such a large amount of reserve 
food that the nurse-plant does not need to make any for itself and 
scarcely protrudes beyond the spore, while the former having no 
embryo to nurse reduces its vegetative part to a single cell. Such 
gametophytes are virtually hysterophytic, and it is interesting to 
observe that types which do not produce macrospores but are 
