GYMNOSPERMS 911 
of large compound leaves, with the general habit of tree- 
ferns and palms (Figs. 198 and 199); or they are like great 
tubers, crowned in the same way (Fig. 200). The tuberous 
stems are often more or less buried, as in our only cycad 
from the United States 
(Florida), illustrated in 
Fig. 200. In ancient 
times cycads were 
very abundant, but 
now they are rep- 
resented by about 
eighty species  scat- 
tered through the ori- 
ental and _ occidental 
tropics. They are especially interesting in their resem- 
blances to ferns, and some of them might be mistaken for 
ferns did they not bear large seeds. In addition to their 
fern-like leaves, they have in the structure of the stem 
many fern characters; and they have coiled sperms with 
many cilia (Fig. 201), as do the ferns. They are very 
interesting to study; but it is easier to obtain the Gym- 
nosperm characters from the other group, whose forms are 
far more familiar and easily obtained. 
Conijers are the common Gymnosperms, often forming 
great forests in temperate regions. Some of the forms are 
widely distributed, as the pines; while some are now very 
much restricted, as the gigantic redwoods (Sequota) of the 
Pacific slope. The habit of the body is quite characteristic, 
a central shaft extending to the very top (Fig. 42). In 
many cases, the branches spread horizontally, with dimin- 
ishing length to the top, forming a conical outline, as in the 
firs. This habit gives the conifers an appearance very 
distinct from that of the other trees. 
Another peculiar feature is the needle-leaf. These leaves 
have a small surface and very heavy protecting cells, being 
Fic. 201.—Two views of the sperm of a cycad, 
showing its spiral form and many cilia. 
