Miller Christy 
298 
discussed fully elsewhere 1 . Thus, in early spring, I have myself seen 
the common Brimstone butterfly visit, not only these two species, 
but also the Cowslip. In Germany, Knuth saw it visit all these 
three species on one single day 2 . Again, all three species are visited 
more or less commonly by various species of Hymenoptera and 
Diptera having tongues long enough to effect their pollination and, 
therefore, to hybridise them. 
Inasmuch as it has been proved by actual experiment in the 
field that hybrids between the Oxlip and the Primrose (namely, 
P. elatior x vulgaris) do arise spontaneously in a state of nature, it 
is a reasonable conclusion that the second of the three Primula 
hybrids mentioned at the outset (namely, P. elatior x veris) also 
arises in the same way. 
This is a very rare hybrid, occurring sporadically only: never 
abundantly anywhere. I doubt if I have seen as many as forty 
plants of it in the forty years during which I have made a study of 
our British Primulas. This rarity is somewhat surprising in view of 
the fact that the Cowslip (unlike the Primrose) grows not uncommonly 
throughout the whole of the Oxlip Area defined by me. The rarity 
of this hybrid is probably due to the fact that the flowering-times 
of its two parent species differ somewhat (the middle of the Cowslip 
flowering period being from two to three weeks later than that of 
the Oxlip, though the flowering periods of the two overlap) 
and that their habitats also differ (the Oxlip growing mainly in 
woods: the Cowslip in meadows); so that there is comparatively 
little probability of hybridisation between them 3 . The hybrid is in 
every way intermediate, in all its characters, between its two parent 
species. So far as I have observed, single (non-pedunculate) flowers 
never occur in this hybrid, its flowers being always borne in umbels 
—doubtless because both its parents normally have umbellate 
inflorescences. As I have seen the hybrid growing in both woods and 
meadows, it seems probable that the female parent may be supplied 
by either species. 
On the same grounds, it is a reasonable assumption that the third 
of the three Primula hybrids mentioned at the outset (namely, 
P. veris x vulgaris) also arises in the same way. 
1 See Journ. Linn. Soc., Bot. 46 (1922), pp. 105-139. 
2 Flower Pollination, 2 (1899), p. 69. 
3 Kerner says, however (Nat. Hist, of Plants, 2 (1902), p. 404), that “ artificial 
pollination between them only occasionally leads to any result.” 
