304 Science of Plant Life 



Diversification among the Angiosperms. The great dif- 

 ferences in the stems of Angiosperms may be realized by call- 

 ing to mind the elm, palm, cactus, dandelion, grape, morning- 

 glory, bamboo, tumbleweed, pondweed, water lily, dodder, 

 and duckweed. The leaves may be simple or divided into 

 leaflets ; and in size they range from the minute scales of the 

 heather to the leaves of the palm and banana, which may be 

 from 20 to 30 feet long. The form, color, and venation of 

 the leaves show a corresponding diversity, so that all shapes 

 and sizes of leaves may be found within the group. The 

 Angiosperms have extensively developed root systems that 

 are capable of anchoring the plants and absorbing water under 

 the greatest variety of soil conditions. The reproductive 

 structures are very diverse and are more complex than in the 

 Gymnosperms. In addition to a great number of methods 

 of vegetative multiplication by leaves, stems, and roots, there 

 is the production of seeds from flowers. In the higher 

 Angiosperms there are brightly colored floral parts which are 

 helpful in securing the transfer of pollen by insects. The 

 seeds are inclosed in fruits which protect the developing ovules 

 and frequently aid in the scattering of the seeds. 



Two great groups of Angiosperms. The Angiosperms 

 naturally fall into two great groups : the monocotyledons and 

 the dicotyledons. These groups have already been discussed 

 (page 209), and only a general summary of their character- 

 istics will be presented here. 



Monocotyledons. The Monocotyledons have their floral 

 parts usually in groups of three (rarely in four) ; the bundles 

 are closed and scattered throughout the pith of the stem; 

 in most forms the veins of the leaves are parallel ; and the 

 embryo has but one well-developed cotyledon. With the 



