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 Monocotyledons 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 g^ 

 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 families of economic im- 

 portance and one family that surpasses 

 all other groups of Angiosperms in 

 number of valuable food plants. 



Cat-tail Family ( Typhaceae) . This 

 family is mentioned because it includes 

 the simplest of the Monocotyledons. 

 They grow in swamps and in the edges 

 of ponds, lakes, and stagnant streams. 

 They have large grass-like leaves and 

 often get 5 or 6 feet high. Their flowers 

 are borne in long fuzzy spikes resembling 

 a cat's tail (Fig. 448). The flowers are 

 monoecious with both calyx and corolla 

 absent. (Fig. 449.) The pistil is com- 

 posed of one carpel containing one locule 

 and only one ovule. The staminate 

 flowers are borne at the top and the pis- 

 tillate flowers below on the spike. The pistil is supported by a 

 stalk or stipe which de: elops hairs that become the brown down 

 of the fruit. The stamens are attached directly to the axis of 

 the spike and are intermixed with hairs. As to whether the 

 simple flowers of the Cat-tails are primitive or are reduced 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 (Xj). 



