368 



THE PANDANALES 



arranged in successive whorls of three parts each, the latter type 

 of flower being especially common. Perigynous, epigynous and 

 irregular flowers are of less common occurrence. The most con- 

 spicuous feature of the monocotyledons is the embryo, which has 

 a single terminal cotyledon and a laterally developed stem tip 

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



B 



FIG. 277. FIG. 278. 



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

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

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



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, be'ing 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. r : A 



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 



