130 A TEXT-BOOK OF GRASSES 



protection, germination or dispersal. In the present discussion the 

 term fruit is used in both senses. 



The fruit of Panicum and allied genera consists of 

 the hard, tightly closed fertile lemma and palea within 

 which is the caryopsis (Fig. 21). Not infrequently the awn 

 of the lemma is involved in the fruit and performs an 

 important function in dispersal or in connection with 

 germination. This is the case with Stipa (Fig. 36), 

 Aristida (Fig. 35), Heteropogen and many Avenese. 

 The fruit may include the surrounding sterile branchlets 

 forming a bur, as in Cenchrus (Fig. 27); a greatly har- 

 dened inclosing bract, as in Coix (Fig. 12); the joints of 

 the rachis in which the spikelet is partially inclosed, as in 

 Tripsacum; or a combination of rachis joint and long- 

 awned sterile spikelets, as in Sitanion and Hordeum. 



Rarely the ovary ripens into some form other than a 

 caryopsis. In a few genera such as Sporobolus and Eleu- 

 sine, it becomes an utricle, the pericarp being thin and not 

 grown to the seed. In many species of Sporobolus, for 

 example S. airoides Torr. and 8. indicus (L.) R. Br., the 

 pericarp tends to split vertically into 2 valves, thus being 

 dehiscent. The pericarp of Eleusine breaks away irregu- 

 larly. The fruit becomes a nut or a berry in certain 

 bamboos. 



163. The seed consists of an embryo at the base on 

 one side and of endosperm occupying the remaining por- 

 tion. If the surface of a caryopsis is examined, the posi- 

 tion of the embryo is outlined as a depressed usually oval 

 area at the base on the front side, that is, on the side 

 facing the lemma. On the opposite side, next the palea, 

 is the mark called the hilum, which indicates the place 

 where the seed was attached to the wall of the ovary 

 (pericarp). The hilum may be elongated if the seed is 



