DEVELOPMENT OF PLANTS 405 



perish after the discharge of their spores, but the pistils increase 

 greatly in size during the ripening of the seed and form con- 

 spicuous brown cylinders (Fig. 280, D). As winter approaches, 

 the pedicel below the ovary and the hairs attached to it become 

 greatly elongated and the sporophyll is thus transformed into 

 a very stable parachute that is easily detached from the spike 

 and capable of floating the seed in even the lightest winds (Fig. 

 281). If this fruit chances to fall in a marsh, the torpedo-like 

 seed after a time falls from the ruptured ovary and sinks in the 

 water. When the growth of the seed is renewed, the base of 

 the cotyledon elongates, pushes off the lid at the end of the seed 

 and curves down so as to bring the root of the embryo in con- 

 tact with the mud. Hairs now develop from the lower part of 

 the cotyledon, anchoring the young plant to the ground while 

 the tip of the cotyledon remains in the seed until the food is 

 absorbed, when it is withdrawn. In the meantime, roots have 

 developed and penetrated the soil and the stem tip begins to 

 elongate, lifting up the cotyledon and making possible the for- 

 mation of other leaves. The curious screw-pines, Pandanus, a 

 large group from the oriental tropics and frequently seen in con- 

 servatories, belong to this order, also the bur reed (Sparganium) , 

 common about marshes and water ways, which is the highest 

 member of the order. 



131. Graminales, the Grass and Sedge Order. — This is one of 

 the largest groups of the Spermatophyta, some 7,000 species 

 being known, and in number of individuals it exceeds all others 

 (Fig. 282). These plants are almost universally distributed 

 over the earth and have become adapted to almost every condi- 

 tion of climate and soil. The ability of these plants, which are of 

 aquatic origin, to establish themselves upon the drier and more 

 diversified land surface doubtless promoted variations and ac- 

 counts in part for the enormous display of forms. The Grami- 

 nales and the palms (Principales) which belong to an order 

 related to Typha are about the only groups of monocotyledons 

 that are associated in sufficient numbers to form striking features 

 of the vegetation of a country. This is particularly true of the 

 Graminales in all lands, where they constitute the principal vege- 



