The Angiosperms 165 



cotyledons, but it has been claimed that traces of 

 such thickening tissues have been found in the seed- 

 lings of many monocotyledons, indicating that its 

 absence in the woody bundles of the mature plant 

 is a secondary condition. While the monocoty- 

 ledons are as a rule less conspicuous than the di- 

 cotyledons in the flora of most regions, there are 

 certain types which are gregarious and predominate 

 over large areas. This is conspicuously true of the 

 grasses in open prairie country ; and in swampy 

 districts, rushes, sedges, etc., may be found to be 

 the principal constituents of the vegetation, and 

 under these conditions are evidently quite able to 

 hold their own in competition with the usually more 

 aggressive dicotyledons. 



Monocotyledonous Flowers. The flowers of the 

 Monocotyledons, as we have already seen, belong 

 to the two principal types, apetalous and petaloid- 

 eous. Of the former, some of the types cannot 

 readily be explained as reductions from petaloideous 

 flowers, and they are in all probability really primi- 

 tive types. Such, for example, are the flowers of the 

 cattail rushes, the bur-reeds, and the screw- 

 pines. The two last, in addition to the simple type 

 of flowers, show marked indications of the more 

 primitive condition of the gametophyte, which is 

 much better developed than in most angiosperms. 

 The arums and palms are also probably old types, 

 not reduced from petaloideous forms, but as in these 

 two families both hermaphrodite and diclinous flow- 



