CHAP, i.] Joseph G. Koelreuter and Konrad SprengeL 413 



hybrids to the original form by the repeated employment of 

 its pollen ; the value of these experiments for theoretical 

 purposes was afterwards fully brought out by Nageli. 



It is impossible to rate too highly the general speculative 

 value of Koelreuter's artificial hybridisation. The mingling of 

 the characters of the two parents was the best refutation of 

 the theory of evolution, and supplied at the same time pro- 

 found views of the true nature of the sexual union. It was 

 shown by his numerous experiments that only nearly allied 

 plants and not always these are capable of sexual union, which 

 at once disposed of Linnaeus' vague ideas in the judgment of 

 every capable person, though it was long before science 

 candidly accepted Koelreuter's results. The plant-collectors 

 of the Linnaean school as well as the true systematists at the 

 end of the i8th century had little understanding for such 

 labours as Koelreuter's, and incorrect ideas on hybrids and 

 their power of maintaining themselves prevailed in spite of 

 them in botanical literature. Hybrids were necessarily in- 

 convenient to the believers in the constancy of species ; they 

 disturbed the compactness of their system and would not fit 

 in with the notion that every species represented an ' idea.' 



Koelreuter's doctrines however did not always fall on un- 

 fruitful soil ; two botanists at least were found in Germany 

 who adopted them, Joseph Gartner the author of the famous 

 Carpology and father of Carl Friedrich Gartner who at a later 

 time spent twenty-five years in experimenting on fertilisation 

 and hybridisation, and Konrad Sprengel who took up Koel- 

 reuter's discovery of the services rendered by insects and 

 arrived at some new and very remarkable results. 



JOSEPH GARTNER made no fresh observations on sexuality 

 himself, but in the Introduction to his ' De fructibus et semi- 

 nibus plantarum ' (1788) he made use of Koelreuter's results for 

 the purpose of distinguishing more clearly between different 

 kinds of propagation, and strengthening his own attack on the 

 theory of evolution. The germ-grains or spores of cryptogamic 



