GJ-UMIFLOM. 233 



is also an entirely submerged plant. The leaves are arranged in whorls on a 

 well-developed stem. Only $ -plants in Europe (introduced about 183G from 



N. Am ). This plant spreads with great rapidity throughout the country, the 

 reproduction being entirely vegetative. Hydrilla, Haliphila, Thalassiu,Enhalus. 



In many of these genera the number of whorls in the flower is remarkably re- 

 duced; for example, in Vallisneria, in the <? -flowers to 2: Pr 3, A (1-) 3, in the 



? to 3 : Pr 3, Staminodes 3, G 3. About 40 species ; Temp, and Trop. 



Family 2. Glumiflorae. 



The hypogynous flowers in trie Juncaceas are completely developed 

 on the petitacyclic, trimerous type, with dry, scarious perianth. Even 

 in these the interior whorl of stamens becomes suppressed, and the 

 ovary, which in Jnncus is trilocular with many ovules, becomes in 

 Lnzula almost uniloculai-, but still with 3 ovules. The perianth in 

 the Cyperaceae and Gramineae is reduced from hairs, in the first of 

 these, to nothing, the flowers at the same time collecting- more 

 closely on the inflorescence (spike) supported by dry bracts (chaff) ; 

 the number of stamens is almost constantly 3 ; stigmas linear; the 

 ovary has only 1 loculus with 1 ovule, and the fruit, which is a cap- 

 sule in the Juncacese, becomes a nut or caryopsis. The endosperm 

 is large and floury, the embryo being placed at its lower extremity 

 (Pigs. 286 B, 291). The plants belonging to this order, with the 

 exception of a few tropical species, are annual or perennial herbs. 

 The stems abore ground are thin, and for the most part have long 

 internodes, with linear, parallel-veined leaves which have long 

 sheaths, and often a ligule, i.e. a membranous projection, arising 

 transversely from the leaf at the junction of the sheath and blade. 

 The underground stems are short or creeping rhizomes. The 

 flowers are small and insignificant. Wind- or self-pollination. 



Order 1. Juncaceae (Rushes). The regular, hermaphrodite, 

 hypogynous flowers have 3 + 3 brown, 

 dry, free perianth - leaves projecting 

 like a star during the opening of the 

 flower ; stamens 3 + 3 (seldom 3 + 0) 

 and 3 carpels united into one gynceceum 

 (Fig. 283) ; the ovary is 3- or 1-locular ; 

 there is as a rule 1 style, which be- 

 comes divided at the summit into 3 

 stigmas, often bearing branches twisted 

 to the right (Fig. 283). Fruit a capsule 



with loculicidal dehiscence. The embryo is an extremely small, 

 ellipsoidal, cellular mass, without differentiation into the external 

 organs. 



