CHAPTER XIX 
PHYLUM XIII. STROBILOPHYTA 
THE CONIFERS 
497. To a large extent this is a phylum of living plants, 
and although many species and some genera have be- 
come extinct, every family is still represented in some part 
of the world. The number of living species is about 400, 
widely distributed throughout the earth. The Conifers 
probably were derived from some of the old Cycads 
(Cordaitales) to which they show some affinities. 
498. In these plants there is a still more marked 
alternation of generations than in the preceding phyla. 
The gametophytes are so minute and short-lived that 
they are rarely seen, while the sporophytes are mostly 
great trees with long-lived perennial roots and stems and 
mostly perennial green leaves also. The phylum may be 
defined as follows: Megaspores and microspores mostly 
borne in homogeneous cones of sporophylls on the 
arboreous sporophytes. Archegonial gametophytes very 
minute, solid, ellipsoid, and permanently enclosed in the 
megaspore, which in turn is retained in the megasporan- 
gium; antheridial gametophyte minute, few-celled, free, 
developing a tubular antherid containing two noncili- 
ated sperms. After the fertilization of the egg and the 
‘formation of the cylindrical, leafy sporophyte, the 
megasporangium, covered by an indusial coat (integu- 
ment), becomes a “‘seed.”” The sporophyte upon escaping 
from the seed in germination grows into a perennial, 
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