g28 PRINCIPLES OF BOTANY, ETC. 
of some particular plants; but unfortunately he has 
given nothing but hypotheses, his observations not 
according with experience. 
Should it not, from the observations made with 
regard to the hybrids of the animal and vegetable 
world, be laid down as a rule, admitting some ex 
ceptions, that all hybrids are productive, but that 
some only want a warm climate, to unfold the male 
semen! I do not attempt to establish this rule as 
quite certain; I should be happy, on the contrary, 
would philosophers consider this subject more ac- 
curately, and attend more to the hybrids of different 
climates, on purpose to settle the point. 
But Koelreuter made some experiments, which 
put the doctrine of LEpigenesis beyond all doubt. 
{ shall only mention one of his observations as an 
instance. He obtained, as we have seen, a hybrid 
from Nicotiana rustica and paniculaia. Nicotiana rus- 
tica was the female plant, paniculata the male. ‘The 
hybrid, like all the others which he brought up, had 
imperfect stamens, and kept the middle between the 
two species. He afterwards impregnated this hybrid 
with Nicotiana paniculata, and got plants, which 
much more resembled the last. ‘This he continue 
through several generations, till in this way, by due 
perseverance, he actually changed the Nicotiana 
rustica into the Nicotiana paniculata. By those and 
other experiments, often repeated, and made in va- 
rious ways and upon other plants, it seems clearly 
established, that there is no pre-formation in plants. 
According to the theory of Epigenesis then, the 
fluids of the male and female ave mixed, and an off- 
an a spring 
