CHAPTER FORTY-EIGHT 



THE ANGIOSPERMS OR FLOWERING PLANTS 



The flowering plants, or angiosperms, have the shortest geo- 

 logical history of all the vascular plants, though they include the 

 largest number of species and the greatest diversity of vegetative 

 forms and reproductive structures. Since Cretaceous times they 

 have been gradually replacing the gymnosperms, until today 

 they are the dominating plants of the earth. 



There are at least 140,000 angiosperms, or about 40,000 more 

 than of all other known species of plants combined. They include 

 herbs, shrubs, vines, and trees, and they vary in size from the 

 duckweed, Wolffia (half the size of a pin head), to the Australian 

 Eucalyptus, 340 feet high. To this variety of forms is added 

 structural, physiological, and chemical diversity that enables 

 the angiosperms to live in almost every habitat on the earth. 

 Consequently we find the angiosperms in control of most tropical 

 forests, the temperate deciduous forests, the prairies, the plains, 

 and the deserts, and forming the undergrowth of nearly all 

 conifer forests. 



With the angiosperms came not only the habit of forming seeds 

 in closed ovularies, but also the production of variously colored 

 bracts and floral leaves surrounding the spore-bearing stamens 

 and carpels. The primitive angiosperm .flowers, represented 

 today by the magnohas and the tulip tree (" yellow poplar "), 

 had the sporophylls spirally arranged like the scales on the 

 cones of conifers. Another primitive type, represented by wil- 

 lows, have the very simple flowers spirally arranged in spikes 

 and catkins. 



Among the floral organs nectaries appeared, usually near the 

 base of the sporophylls. The Paleozoic landscapes may have 

 rivaled our own, with their varieci textures and shades of green, 

 but they were devoid of that color interest which flowers added 

 to the Tertiary and more recent landscapes. 



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