PHANEROGAMIA. 243 



from the first internodes of the stem (w'", w", w'). The 

 first leaf above the cotyledon is quite small {b), and each 

 succeeding one becomes larger and larger until the full size 

 is reached. 



514. Monocotyledons include about 18,000 known species 

 which are by the latest authorities arranged under thirty- 

 four orders. These orders, moreover, are brought together 

 in seven groups (series). In the following tabular presen- 

 tation only the more obvious characters are given. 



Series I. Glumaceae. — Perianlh chaff-like or none. Ovary single, 

 one-ovuled. Seeds with endosiienn. 



Order 1. The Grasses (Graiiiinese). — Herbaceous or rarely woody 

 plants with rouTid, jointed, and mostly hollow stems, bearing alter- 

 nate two-ranked leaves with split sheaths. Species 3100 to 3300, 

 distributed in all climates. 



Older 2. The Sedges (03'perace8e). — Herbaceous plants with three- 

 angled solid stems Ijearing ihi'ee-ninked leaves with entire sheaths. 

 The 2200 species are distributed throughout the world. 



Orders 3 to 5 (RH.sliaceae, Cenlrolepidese, Eriocaulonaceae) include 

 five or six hundred grass-like or lusli like, mostly tropical plants. 



Series II. Apocarpese, — Perianth in one or two series or none. Ova- 

 ries single, or many always distinct. Seeds without endosperm. 



Order 6, the Pondweeds (Naiadacese), Order 7, the Water-plan- 

 tains (A-lismacese), Order 8 (Triurideae), mostly common water- 

 plants, aggregating about 200 species. 



Series III. Niidiflorae. — Perianth none. Ovaries single, or many 

 united. Seeds mostly with endosperm. 



Order 9. The Duckweeds (Lemnacese). — These are the smallest of 

 flowering plants, and consist of floating discs generally bearing one 

 or a few roots beneath. About twenty species are known, half of 

 which occur in the United States. 



Order 10. The Aroids (Aroidese). — Herbs often large a^d palm-like 

 in appearance, with large leave's having reticulated venation. There 

 are about 900 species, distributed mostly in tropical countries, where 

 they sometimes attain a height of several metres (6-13 feet); in tem 

 perate climates they are much smaller. 



Order 11. The Cattails (Typhacese).— This small order is well rep- 

 resented by the well-known Cat-tail Flag of our ponds. 



