DEVELOPMENT OF PLANTS 



401 



type of flower being especially common. Perigynous, epigynous 

 and irregular flowers are of less common occurrence. The most 

 conspicuous feature of the monocotyledons is the embryo, which 

 has a single terminal cotyledon and a laterally developed stem tip 



Fig. 277. Fig. 278. 



Fig. 277. Leaf of Solomon's seal with closed venation, entire margins, 

 and sessile upon the stem, i. e., without petiole. 



Fig. 278. Cross-section of stem of rush: v, vascular bundles; st, stereome. 



(Fig. 279). Generally the root and stem tip are set free from 

 the seed by the elongation of the basal portion of the cotyledon, 

 while the cotyledon remains in contact with the endosperm as a 

 food-absorbing organ, being often highly modified to perform 

 this work. An examination of a few of the more important 

 orders will give a better idea of the characteristics and variations 

 of the monocotyledons. 



130. Pandanales, the Cat-tail Order. — The cat-tail, Typha, 

 may be taken as an illustration of this order (Fig. 280). These 

 plants live in wet and marshy places and present several varia- 

 tions that adapt them to such conditions. The main stem is a 

 rhizome that branches through the mud and sends up each spring 

 leafy stems. The rhizome grows on from year to year, and 

 owing to the decay of the older portions, the branches become 

 independent plants. In this way a single plant may spread and 

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