Chapter 13 



GYMNOSPERMOUS PLANTS- 

 CONIFERS AND THEIR ALLIES 



Higher Plants With Chlorophyll; With True Leaves, Stems, and 

 Roots; With Vascular Tissues; With Exposed (Naked) Seeds; 

 Forming Multicellular Embryos (Subkingdom Embryophyta) 



GENERAL CHARACTERISTICS OF GYMNOSPERMS 



L The gymnosperms belong to the subkingdom Embryophyta; the 

 phylum Tracheophyta; subphylum Pteropsida; class Gymnospermae (jini- 

 no -spur' me) (Gr. gymnos, naked or exposed; sperma, seed) because the 

 seeds are produced on the exposed (naked) surface of the megasporo- 

 phylls and are not protected by an ovary w^all, as in angiosperms. 



2. Gymnosperms are usually rather large, woody, perennial plants 

 which are mainly evergreen (retain leaves more than one growing sea- 

 son) . Certain types may be short and shrubby. 



3. Gymnosperms possess true roots, stems, and leaves. In the cone- 

 bearing evergreens the leaves may be needlelike or scalelike. 



4. The sporophyte generation is large, complex, and independent, 

 while the gametophyte generation is much smaller (microscopic) and 

 parasitic upon the sporophyte. 



5. Cones composed of sporophylls are usually present; in the conifers, 

 the male and female cones may be present on the same plant {monecious) 

 or on different plants (diecious) , depending upon the species. 



6. Ovules (immature, undeveloped seeds) and true seeds are borne 

 exposed (naked) on female megasporophylls (a single megaspore is re- 

 tained within the megasporangium where the female megagametophyte 

 develops). The sporophylls often form cones. 



7. Two kinds of spores are formed (heterosporous) ; namely, micro- 

 spores, which produce male microgametophytes, and m,e gas pores, which 

 produce female megagametophytes. (The two spores may be the same 

 size or the microspores may even be larger than the megaspores, yet they 

 produce different types of gametophytes.) 



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