24 NATURAL HISTORY OF PLANTS. 



the genus Erica, nearly 200 species, of Stapelia above 50, of Ixia 

 and Gladiolus 58, of Protea above 70 () f Mesembryanrhemum 

 about 180, not to mention other genera which likewise contain" 

 numerous species. The great resemblance between some oftbt.se, 

 which m :kes it difficult to find characters to distinguish ihem by, 

 gives some colour to the supposition. 



It is now well known, that fertile hybrids are not uncommon 

 in the vegetable kingdom. We find this occurrence in our gar- 

 dens, and cannot deny that it may sometimes happen in the fields. 

 Nature, however, has wisely provided, that in a wild state an inti- 

 mate mixture cannot easily take place in plants. Those that nearly 

 resemble one another, we find growing in very distant regions, 

 fiower 1 ';; at different times, or placed in dissimilar situations. It is 

 only congenerous plants that can mix and produce hybrids; nor 

 can even that happen, unless many species of a genus grow in a given 

 spot. Let us give an example of this position. We have, in 

 various places, three species of Scrophularia growing wild ; namely, 

 the Scrophularia verna, nodosa, and aquutica. The first grows 

 about the villages in hedges, and flowers in the spring; the second 

 is found in moist pastures, and flowers a month later : the third 

 grows in rivers, marshes, and ponds, and flowers a month later than 

 the second. Other species of this genus, which resemble the above, 

 grow in Italy, Siberia, in the East, in North America, &c. By none 

 of these can any spurious breed be produced in their native situa- 

 tions. But if we bring all the foreign and indigenous species of the 

 genus together, and place them in a botanic garden, would it be 

 surprising if, in a soil to which they are not accustomed, some should 

 flower sooner and some later than is natural to them, and by the 

 additional means of the insect tribe, flying from one to another 

 loaded with impregnating pollen, a hybrid should appear among 

 them ? We shall soon find a number of plants that never origina ly 

 grew wild, but owe their existence solely to botanic gardens. 



The numerous varieties of our fruits have certainly had their ori- 

 gin in this spurious method of impregnation, and perhaps some that 

 pass for species have been produced in the same way. It is pro- 

 bable that Pyrus dioica, Pollveria, and prunifolia, owe their 

 existence to such mixtures. 



But were it even doubtful whether new plants were ever produced 

 by mixture, we have perhaps a still more important conclusion to 



