Gymnospermous Plants — Conifers and Their Allies 201 



8. Pollination occurs by wind, the pollen grains landing near, or in, 

 the micropyle (little opening) of the ovule and forming a pollen tube 

 leading to the egg. 



9. In gymnosperms, single fertilization occurs in which one sperm is 

 involved in fertilizing the egg, in contrast to double fertilization as it 

 occurs in the angiosperms (flowering plants). 



10. In pine trees, the lapse of time between pollination and subsequent 

 fertilization (actual union of the sex gametes) is a marked feature. For 

 example, if pollination occurs in June, fertilization may not ordinarily 

 occur until July of the next year. This time lapse varies with the species, 

 locality, etc., but usually a year elapses between pollination and fertiliza- 

 tion. After fertilization the seed develops rather rapidly, reaching ma- 

 turity by the end of the year in which fertilization occurs. 



11. Gymnosperms are considered to be higher plants than ferns, horse- 

 tails, and club "mosses" because (1) of the two kinds of cones which 

 bear, respectively, male microsporophylls and female megasporophylls ; 

 (2) of a temporary retention of the developing microgametophytes (pol- 

 len grains) in the microsporangium; (3) of a retention of the megaspore 

 and the megagametophyte in the megasporangium (nucellus) ; (4) of 

 the direct parasitism of both male microgametophyte and female mega- 

 gametophyte upon the large, conspicuous sporophyte; (5) of the develop- 

 ment of a pollen tube and the establishment of the seed habit. 



CONIFERS 



Pine Tree [Pinus) (L. pinus, cone bearing) (Figs. 52 and 53).- — The 

 conifers belong to subphylum Pteropsida, class Gymnospermae (jim no- 

 spur' me) (Gr. Gymnos, naked; sperma, seed) ; order Coniferales (ko ni- 

 fer-a'lez) (L. conus, cone; jero, to bear) because most of them bear 

 cones composed of sporophylls (sporangium-bearing leaves). There are 

 over 500 species of conifers, including the various species of pine, spruce, 

 fir, juniper, cedar, hemlock, larch, yew, cypress, redwoods, etc. The 

 leaves are simple and are either needlelike or scalelike. Conifers are often 

 referred to as "evergreens" because most of the leaves on many species 

 remain throughout the year. A few, such as the bald cypress and larch 

 (tamarack), are deciduous. All are woody and usually are trees, al- 

 though some are shrubs. Some of the oldest and largest plants are 

 conifers; for example, the giant sequoia trees of California may be over 

 30 feet in diameter, 300 feet tall, and 4,000 years old; the redwoods may 

 be 15 feet in diameter, 300 feet tall, and 1,000 years old. 



