CHAPTER XX 



SOME LEADING FAMILIES OF FLOWERING PLANTS AND 

 THEIR USES 1 



MONOCOTYLEDONS 



307. Introductory. When people speak of flowering plants 

 they usually mean angiosperms, or plants with a closed ovary 

 (Fig. 101), including all the families of monocotyledons and 

 dicotyledons. As shown in Sects. 302-306, these groups oc- 

 cupy the highest place in the plant world. 



Monocotyledonous plants usually have seeds with one coty- 

 ledon, flowers with their parts in threes, leaves with parallel vein- 

 ing (Fig. 268), and stems with the woody bundles not forming a 

 hollow cylinder about a central pith (see Fig. 38). 2 



Dicotyledonous plants usually have flowers with their parts 

 mostly in fives (not in threes), seeds with two cotyledons, leaves 

 with netted veining (Fig. 270), and stems with the woody bundles 

 arranged at first in a hollow cylinder about a central pith (see 

 Fig. 30). 3 



1 TEACHERS' NOTE. There is included in this chapter a great deal of infor- 

 mation about the families presented and their economic value. Generally it 

 will not be found advisable to use the entire chapter as a basis for assigned 

 lessons. Sometimes it should be so used, but more often it will be found val- 

 uable for collateral reading and as a source of information regarding many 

 questions that arise in an elementary course. A few figures of plants from 

 families not mentioned in the text have been introduced for the sake of 

 illustrating additional types. 



2 There are occasional exceptions to these statements ; for instance, most 

 seeds of the Orchis family have no cotyledon, the pondweeds (Potamogeton) 

 have flowers with parts in fours, the leaves of Trillium, Smilax, jack-in-the 

 pulpit, and plants of the Yam family are netted-veined. 



3 A few dicotyledons, like Cyclamen, have seeds with only one cotyledon, 

 and a few others, like Indian pipe (Monotropa), have no cotyledons. Some 

 parasites have hardly any stem, but are practically flowers attached to the 

 root or stem of the host by numerous haustoria. 



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