INTRODUCTION TO CRYPTOOAMIC BOTANY. 63 



individual, without any intermediate rest ; that impregnation 

 takes place by spermatozoids, and not by a pollen tube ; that the 

 embryo grows in an entirely diflerent way ; that the radicle does 

 not point to the foramen, and that, after all, the mode of growth 

 in the stem is totally different. When, moreover, we weigh the 

 arguments, as to the comparative dignity of Conifers, and see 

 that they are certainly not inferior to a host of other Phoeno- 

 gams, some of the highest of which have fruit of the very 

 simplest kind, though we may recognise very curious resem- 

 blances, and though we may admit that these are decided 

 analogies, we shall not be prepared to ascribe any close affinity 

 between them. 



51. The various theories which have been mooted from time 

 to time respecting spontaneous or equivocal generation, have 

 been, for the most part, grounded on the development of 

 Cryptogams, and of those animals which are lowest in the 

 scale of creation. Such fancies, however, have by no means 

 been confined to them, for no less remarkable phsenomena 

 occur occasionally among Phasnogams, a few of which may be 

 mentioned. It is, for instance, a well-known fact that on our 

 eastern coast, when land is taken in from the sea by means of 

 embankments, and the tide finally excluded, the first vege- 

 tation which appears is a crop of white clover. When heath 

 is burned in many districts the same plant makes its appear- 

 ance. Sisymbrium Trio covered every ruin after the Great 

 Fire of London in 1666, and in many parts of the United 

 States the certain follower of extensive conflagrations in 

 the forests is Lactuca elongata, which, in consequence, is 

 known by the name of fire-weed. Now it would be quite as 

 rational to suppose spontaneous generation in these cases as in 

 those of Fungi, the lower Alga3, or Mosses. The woods in my 

 own neighbourhood are sometimes blue with Columbines the 

 year after the underwood is cut, though it may be difficult to 

 find a plant at other times ; and it is notorious that certain 

 Orchids, as Ophrys apifera, Epipactis latifolia, &c., appear 

 only periodically in situations which are sometimes quite 

 naked, sometimes covered with Biiishwood.* But in these 



* Some of the Orchids produce bulbs which are many years before 



