Chapter 14 



ANGIOSPERMOUS PLANTS— FLOWERING PLANTS 



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

 Roots; With Vascular Tissues; With Enclosed Seeds; Forming 

 Multicellular Embryos (Subkingdom Embryophyta) 



GENERAL CHARACTERISTICS OF ANGIOSPERMS 



L Angiosperms, or flowering plants, belong to the phylum Tracheo- 

 phyta; subphylum Pteropsida, class Angiospermae (an jio -spur' me) 

 (Gr. angios, vessel or enclosed; sperma, seed) because the ovules and 

 seeds are enclosed by megasporophylls (carpels) (Fig. 71). At maturity, 

 the latter constitute the fruit. 



2. Angiosperms constitute the dominant, economically most important, 

 and the largest class in the plant kingdom, comprising nearly 200,000 

 species in approximately 10,000 genera. 



3. The angiosperms are widely distributed on the earth, where they are 

 primarily terrestrial, although a few are aquatic (hydrophytes). 



4. Angiosperms possess true leaves, stems, and roots. 



5. Angiosperm possess flowers and true seeds (Fig. 71) . 



6. The angiosperm plant, whether it be corn, bean, sunflower, or a 

 deciduous tree, is the sporophyte with its roots, stem, leaves, and flowers. 

 The cells of the sporophyte contain the double number (diploid) of 

 chromosomes (2N). 



7. The sporophyte produces two types of spores (heterospory), al- 

 though, as in the gymnosperms, the microspores may actually be larger 

 than the megaspores. 



8. The gametophyte generation is represented by the (female) mega- 

 gametophyte and the (male) microgametophyte. The microgameto- 

 phyte is represented by the pollen grain and the pollen tube with its 

 three cells (two sperms and one tube nucleus). The megagametophyte 

 is the embryo sac consisting of seven cells (one e^g, two nonfunctional 

 synergid cells, three nonfunctional antipodal cells, and two polar nuclei). 

 The two polar nuclei fuse with one sperm nucleus to form the endosperm 

 (food) whose cells contain the unique, triple number of chromosomes 

 (3N). The two synergid cells are thought to be remnants of the arche- 



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