184 



BOTANY. 



resembling closely the corolla of a morning-glory or petunia. 

 The stamens are usually more numerous than the sepals, and 

 the pistil, though composed of several carpels, has, as a rule, 

 but a single cavity with the ovules arising from the base, 

 though sometimes the ovary is several celled. 



FIG. 98. Types of Centrospermse. A, plant of spring-beauty, Claytonia 

 (Portulacacese) , x % B, a single flower, x 1. C, fruit, with the sepals re- 

 moved, x 2. D, section of the seed, showing the curved embryo (em.), x 5. 

 E, single flower of smart-weed, Polygonvm (Polygonacese), x 2. F, the 

 pistil, x 2. G, section of the ovary, showing the single ovule, x 4. H, sec- 

 tion of the seed, x 2. /, base of the leaf, showing the sheath, x 1. J, flower 

 of pig-weed, Chenopodinm (Chenopodiacese) , x 3 : i, from without; n, in 

 section. K, flower of the poke-weed, Phytolacca (Phytolaccacese) , x 2. L, 

 fire-pink, Silene (Caryophyllacese) , x %. M, a flower with half of the calyx 

 and corolla removed, x 1. JV, ripe fruit of mouse-ear chickweed, Cerastium 

 (Caryophyllacese) , opening by ten teeth at the summit, x 2. 0, diagram of 

 the flower of Silene. 



The first family (Polygonece) is represented by the various 

 species of *Polygonum (knotgrass, smart-weed, etc.), and among 

 cultivated plants by the buckwheat (Fagopyrum). The goose- 

 foot or pig-weed (Chenopodium) among native plants, and the 

 beet and spinach of the gardens are examples of the family 



