Independently of the question of fertility, the offspring of species and of varieties when crossed may be compared in several other respects.

Gartner, whose strong wish it was to draw a distinct line between species and varieties, could find very few, and, as it seems to me, quite unimportant differences between the so-called hybrid offspring of species, and the so-called mongrel offspring of varieties.

And, on the other hand, they agree most closely in many important respects.

I shall here discuss this subject with extreme brevity.