MONOCOTYLEDONS 



193 



lake, stream, and even the sea ; they occur as giant trees 

 and lowly herbs, as epiphytes and climbers, as insect- 

 consumers and degraded parasites; their potentialities 

 seem to be practically limitless. 



The Angiosperms occur in two natural classes, the 

 Monocotyledons and Dicotyledons. Although there 

 is similarity of structure in the two classes, there are 

 radical distinctions which make it 

 difficult to define their relation- 

 ship. 



Monocotyledons. 



Cotyledons are seed-leaves ; they 

 are developed in the embryo while 

 it is still enclosed in the seed, and 

 they are primary — i.e., they are 

 the first to appear when the seed 

 germinates. Fig. 62 is a drawing 

 of a Wallflower seedling in which Fig. 62. —Seedling 

 c,c, are the cotyledons. The reader ^^° WER ' (AftER 

 will note that they are different c , c , cotyledons; s , stem; 

 from the later leaves. The Wall- G, G, level of ground; 

 flower is a Dicotyledon, for it has r ' TO A ot; hyp \' hypoc °- 



J ' tyledonary stem. 



two seed-leaves. As the term 

 implies, the Monocotyledons produce but one seed-leaf. 

 The possession of a single cotyledon is the fundamental 

 distinction of the Monocotyledons; but there are other 

 characters by which they are readily distinguished. 

 Unlike Dicotyledons and Gymnosperms, they have no 

 definite root system due to the development and branch- 

 ing of the main root; as the plant develops the growth 

 of the main root stops, and its function is assumed by 



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