ENDOGENS. 123 



The embryo of Endogens has but a single cotyledon, 

 or seed-lobe, on which account they are often termed 

 Monocotyledons. Acrogens have no seed-lobe, but cel- 

 lular spores, and are called acotyledons, (from the Greek 

 a, privative, and kotyledon, something hollow,) while Ex- 

 ogens have two seed-lobes, and are dicotyledons. 



The veins in the leaves of Endogens are generally 

 parallel, or straight, (Fig. 48,) and do not 

 form a net-work, and the parts of the flower 

 are arranged in sets of threes, or of some 

 multiple of three. 



2. Exceptions to the parallel venation of 

 leaves in Endogens have been placed by 

 Lindley in a class by themselves the Dic- 

 tyogence, (from dictyon, a net, and gennao, to 

 produce ;) in allusion to the reticulation of 

 the leaves. They comprise the Yam tribe, 

 (Dioscoreacece^) the Sarsaparilla family, (Smi- 

 lacece^) and the Trillium family, ( Trilliacece.} 

 The other classes or sub-classes are, I. Pe- 

 taloidece, or Florida, in which the flowers 

 consist either of a colored perianth (a floral 

 envelope) or of scales arranged in a whorl. 

 2. Glumiferce, in which the flowers have 

 imbricated bracts or scales, called glumes. 

 This includes the two orders of grasses and 

 sedges. The Petaloidece are divided into 

 three sections: i. Epigynce, having perfect 

 flowers, and a superior perianth, (ovary infe- 



J FIG. 48.- Endog- 



rior,) as Orchids, Gingers, Irids, Amarylids, enous Le af, 



T , ing parallel vena- 



etc. ; 2. Hypogynce, having perfect flowers tion. 



