BOTANY. Y3 



species. Ex. Naias, Zannichellia, Potamogeton, Ruppia, Zostcra, all of wliicli 

 have North American representatives. 



Potamogeton natans, or common pondweed, is abundant along the shores 

 of still waters {pi. 55, fig. 1), «, the plant ; 6, a flower ; c, a sepal seen from 

 behind ; d, the same witlv the stamen from the inside ; e, the four pistils ; 

 f, a fruit ; g, longitudinal section of the same, j^ostera niarina {fig. 3), a, 

 a plant reduced ; /;, the upper part of a fertile branch ; c, an opened spatha 

 with the inclosed spadix ; t/, the lower part of a fruit-bearing spadix in the 

 spatha; e, an anther from behind ; /, ovary ; g, ovary opened, showing the seed ; 

 Ä, the seed ; i, section of the seed showing the embryo. 



Order 14. Aroide.e, the Arum Family. Flowers generally unisexual, 

 rarely bisexual, inclosed within a spatha, and usually on a spadix, having 

 male flowers at its upper part, female below, and abortive flowers between 

 them. Perianth either 0, or in the ? flowers rudimentary and scaly. 

 Stamens definite or 00, hypogynous ; anthers extrorse. Ovary free, one- to 

 three- or more-celled ; ovules solitary or numerous ; style short or ; stigma 

 simple. Fruit succulent or dry, indehiscent, uni- or pluri-locular : seeds one 

 or several ; embryo in the axis of fleshy or mealy albumen, sometimes with 

 a lateral cleft for the plumule ; radicle usually next the hilum. Herbaceous 

 or shrubby plants, often with tubes or creeping rhizomes, leaves sheathing 

 at the base, and having parallel or branching veins. They occur in dry and 

 marshy places, and in lakes in various parts of the world, abounding in the 

 tropics. 



This order has l)een variously subdivided ; the most convenient division for 

 our purpose, hoAvever, is into four sub-orders. 



»Sub-order 1. Pistiem {Lemnacece) or Duckweeds. Flowers j ? naked, 

 inclosed in a spatha without a spadix, ovary one-celled, ovules two or more, 

 fruit membranous or capsular. Examples : Pistia, and Lemna or duck- 

 weed. 



Sub-order 2. Acorecc. Flowers 5 having usually a scaly perianth, ar- 

 ranged on a spathaceous spadix, ovules one or more, fruit a berry. Examples : 

 Symplocarpus (S. foetidus or skunk cabbage) ; Orontium (0. aquaticum, never 

 wet, or Golden club) ; and Acorus. A species of this latter genus, Acorus 

 calamus, found both in Europe and America, furnishes the calamus or sweet 

 flag, so much sought after by boys, and a favorite food of the nmskrat (Fiber 

 zibethicus). This specious of Acorus is shown m pi. 55. fig. 4; a, an entire 

 plant ; 6, a spadix ; c, a flower from above ; d, the same from below ; e, an 

 unripe fruit ; /, the same in vertical and g in transverse section ; A, a leaf 

 cut across (right hand of the plate). 



Sab-order 3. Typhineae. (Typhaceae). Bulrushes or Cat-tails. Marsh 

 herbs, with nerved and linear sessile leaves, and monoecious flowers on a 

 spadix or in heads, destitute of proper floral envelopes. Fruit nut-like when 

 ripe, one-seeded. Seed suspended, anatropous ; the embryo straight in 

 copious albumen. There are but two genera, Sparganium and Typha. 

 Typha latifolia is the common cat-tail of the swamps ( pi. 55, fig 5) ; a, 

 the spadix with its spatha ; b, a cross-section of the male spadix ; c, a male 

 flower. 



IS 



