GRASS FAMILY 



495 



Some other well-known weeds of the family are the Cockle- 

 burs, Ragweeds, Ironweeds, Spanish Needles, Wild Lettuce, 

 and Beggar-ticks. 



Monocotyledons 



Among Monocotjdedons about 25,000 species are recognized, 

 which are distributed among 42 families. They are less than 

 one-fourth as numerous as the Dicotyledons. As previously 

 stated, Monocotyledons differ from 

 Dicotyledons in having flowers with 

 parts usually in threes or sixes, leaves 

 with parallel veins except in rare cases, 

 and vascular bundles with the scattered 

 arrangement. The Monocotyledons 

 contain a few famihes of economic im- 

 portance and one family that surpasses 

 all other groups of Angiosperms in 

 number of valuable food plants. 



Cat-tail Family ( Typhaceac) . — This 

 family is mentioned because it includes 

 the simplest of the Monocotyledons. 

 They are aquatic plants, growing in 

 groups in swamps and wet places. Some 

 get as high as one's head, and in the 

 late summer and fall, when their in- 

 florescences resembhng a cat's tail are 

 well formed, they are conspicuous plants 

 {Fig. 44-8) • The flowers are monoecious 

 and have neither caljrx nor corolla {Fig. 

 449)- The pistil is composed of one 

 carpel containing one locule and only 

 one ovule. The staminate flowers are 



borne at the top and the pistillate flowers below on the spike. 

 The pistil is supported by a stalk or stipe which develops hairs 

 that become the brown down of the fruit. The stamens are at- 

 tached directly to the axis of the spike and are intermixed with 

 hairs. As to whether the simple flowers of the Cat-tails are primi- 

 tive or are r(Hluced forms of more complex flowers is not known. 



Grass Family {Gramineae). — The Grasses constitute one of 

 the largest families of Angiosperms and are widely distributed 



Fig. 448. — The com- 

 mon Cat-tail {Thypha 

 latifolia), showing the 

 terminal spikes of flowers 

 consisting of staminate 

 flowers above and pistil- 

 late flowers below (X |). 



