236 



PRACTICAL COURSE IN BOTANY 



341 342 



Figs. 341,342.— 

 Unisexual flowers of wil- 

 low : 341, staminate; 

 342, pistillate. 



shown that the first step taken by the breeder to secure this 

 result is to render the flower incapable of self-fertilization, 

 by removing the stamens. Nature ac- 

 complishes the same purpose ])y the more 

 effectual expedient of providing imper- 

 fect, or unisexual flowers, in which sta- 

 mens only, or pistils only, occur in the 

 same flower. When the stamens alone 

 are present, the flower is said to be stam- 

 inate, or sterile, because it is incapable 

 of producing seeds of its own, though its 

 pollen is a necessary factor in seed pro- 

 duction. If, on the other hand, the 

 ovary is present and the stamens absent, 

 the flower is pistillate and fertile ; that is, capable of produc- 

 ing fruit when impregnated with pollen. Sometimes both 

 stamens and pistils are wanting, as 

 in the showy corollas of the garden 

 "snowball," the hydrangea, and 

 the rays of the sunflower. Such 

 blossoms: are said to be neutral, 

 from the Latin word neuter, mean- 

 ing neither, because they have 

 neither pistils nor stamens. They 

 can, of course, have no direct part 

 in the production of fruit, but are 

 for show merely. (231.) 



268. Moncecious and dicecious 

 plants. — When both kinds of 

 flowers, staminate and pistillate, 

 are borne on the same plant, as in 

 the oak, pine, hickory, and most of 

 our common forest trees, they are 

 said to be monoecious, a word which 

 means " belonging to one household"; when borne on sepa- 

 rate plants, as in the willow, sassafras, and black gum, tliey 



Fig. 343. — Twig of oak with 

 both kinds of flowers : /, fertile 

 flowers ; s, s, staminate ; a, pis- 

 tillate flower, enlarged ; b, verti- 

 cal section of pistillate flower, 

 enlarged ; c, portion of one of the 

 sterile aments, enlarged, showing 

 the clusters of stamens. 



