T H E 
HEW PHYTOIiOGIST. 
Vol. i., No. 4 
April 19 TH, 1902 
SOME RECENT WORK ON HYBRIDS IN PLANTS. 
By V. H. Blackman. 
HE study of hybrids* has been for a long time a field of work 
very much neglected by botanists, and it is only in quite 
recent years that interest has revived in the subject. Yet 
investigations on the crossing of plants were once, in pre-Darwinian 
days, prosecuted with the greatest vigour, as the works of Kolreuter, 
Gartner, Naudin and others show. The two first-named observers 
practically devoted their lives to the subject of the artificial 
production of crosses between various forms of plants. In spite 
however, of the large amount of time and labour expended in these 
researches, no general conclusions seemed forthcoming. The 
form of the hybrid was found to vary within very wide limits, so 
that it might be almost exactly like one of its parents (the false 
hybrids of Millardet), or it might be almost exactly intermediate 
between the two, but there seemed no clearly recognisable law 
relating any of the characters of the hybrid to those of the parents. 
Again, in very many cases there was shown to be a certain degree 
of sterility in the hybrids produced by crossing forms which are 
commonly accepted as “ species,” but that this sterility is in universal 
contrast to the perfect fertility of “varieties” when crossed, a view 
strongly held by both Kolreuter and Gartner, is not supported by 
the evidence. Kolreuter was compelled to reduce ten accepted 
species to the rank of varieties owing to their being quite fertile 
together. It is also well known to horticulturalists that many 
hybrids between “species” are perfectly fertile together under 
suitable conditions and can be grown in large numbers. It was 
* The term “hybrid” is in the present state of our knowledge 
incapable of exact definition. It used to be applied only to 
the result of a cross between different species, but is now more 
generally used (as in this paper) for the result of a cross between 
forms sufficiently dissimilar to be considered as belonging to 
distinct species, races, varieties etc.; as, however, none of these 
categories are at present capable of exact definition, the term 
hybrid itself is not definable. 
