10 



and even these can only be produced amongst closely allied plants, for if they 

 are too widely separated the transmitted pollen would have no effect. As 

 already indicated, an almost infinite variety of devices are employed to ensure 

 this desirable object, the most certain and efficacious being the complete 

 separation of the two organs, and their development on distinct and different 

 plants. By this arrangement one-half of the individual plants of a species 

 will produce stamens only, which will be known as stameniferous or staminate, 

 whilst the other half will bear pistils only and be called pisfcilliferous or pistil- 

 late. Yvom what has been already explained, it will be clearly understood that 

 these latter only are, or can be the fruit-bearing portion. This class of plants 

 is called dioecious, because the sexes are located in two houses. To this 

 catagory a large and apparently increasing number of plants belong, such as 

 the whole family of willows and poplars, also various common plants, which 

 derive their specific name from this peculiarity, such as the Eed Campion 

 {Lychnis dioica), the Marsh Yalerian ( Valeriana dioica), the Mountain Ever- 

 lasting (Antennaria dioica), the Common Nettle (Urtica dioica), and num- 

 erous others. A modification of this provision is manifest in another large 

 class of plants known as monoecious, in which the stamens and pistils are 

 produced on different parts of the same plant, therefore a portion of the 

 blossoms on a plant are staminate only, whilst the rest are pistillate or fruit- 

 bearing. A great many of our well-known forest trees belong to this class, 

 such as the oak, beech, chesnut, hazel, birch, firs, &c, also the very extensive 

 order of the sedges [car ex). Such plants have rarely conspicuous flowers in 

 the ordinary sense of the word, with largely developed calyx and showy 

 corolla, the stamens being usually clustered together in catkins, and after 

 they have shed their pollen they shrivel, wither, and drop off, leaving the 

 pistillate flowers to mature and perfect the fruit. In these two classes it is 

 evident that cross-fertilisation must be the rule. But in the large number 

 of common and conspicuous flowers, which are called complete or perfect, 

 because the stamens and pistils are aggregated together in the same blossom 

 (hence known as hermaphrodite), the same result is not so apparent. 



Besides these three types of flowers there are a few plants, such as the 

 common ash, which are known as polygamous, because in their own persons 

 are united the characteristics of all the three. Thus in a grove of ash trees, 

 a certain proportion will be found producing staminate flowers only, these 

 are readily recognised in autumn by the absence of all fruit. Another section 

 bear perfect pistillate flowers, but the stamens are abortive containing no 

 potent pollen, these are easily distinguished by the numerous clusters of fruit 

 with which the branches are ornamented in autumn, remaining well into the 

 winter. Whilst the third portion produce perfect but not so fruitful flowers, 



