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same 1 . Obviously, however, it would be doubly satisfactory to have 
the confirmatory evidence of experiments carried out actually in 
the field 2 . The chief difficulty in following the latter (natural) method 
lies in the very long period it is necessary to allow when experi¬ 
menting with the two species named; for both grow in woods and 
both flower fully only when these woods are cut down, which is done 
only at intervals of from twelve to fifteen years; so that it is necessary 
to wait at least that time before the result of such an experiment 
can become apparent. 
The hybrid in question (namely, P. elatior x vulgaris) is little 
known to British botanists, though it was long since met with and 
definitely recognised upon the Continent. It is apparently the 
P. media of Petermann, the P. digena of Kemer 3 , the P. elatiori- 
officinalis of various writers, and has also been known under other 
names; but the synonymy of all the three Primula hybrids mentioned 
herein is confused absolutely beyond hope of disentanglement. The 
first to call attention to its occurrence in this country was, I believe, 
the late G. S. Gibson, of Saffron-Walden 4 . Later, I myself pointed 
out more fully the facts as to its occurrence in Britain 5 . I showed 
that it occurs abundantly round the margins of the two Oxlip 
“Districts” defined by me. Here alone the Oxlip comes in contact 
with the Primrose, which grows in profusion all round, but (for a 
reason I have attempted to explain elsewhere 6 ) does not grow within 
these Districts. It is the only one of the three Primula hybrids which 
is ever to be seen in abundance at any one spot 7 . 
1 See Knowledge, 39 (1916), pp. 113—117. 
2 I had long been familiar with the fact that hybrids between the two 
species named arise spontaneously in gardens in which Oxlip plants have been 
introduced among a number of Primrose plants. Thus, in May 1883, I sowed 
some Oxlip seed in a garden at Chignal St James, near Chelmsford, in which 
there were many Primrose plants. It produced nineteen plants; and, within a 
year or two, obvious hybrids between the two species appeared. Some Oxlip 
plants were still growing in the garden nearly a quarter of a century later (on 
13th April 1906), together with some of the hybrids. Again, in April 1884, 
I saw in the garden of the late Mr James H. Tuke, at Bancroft, Hitchin, in 
which there were growing both Oxlips and Primroses, a pink-flowered Oxlip, 
evidently a hybrid with some red-flowered Primrose. A red-flowered garden 
form of the Oxlip, no doubt of similar hybrid origin, is mentioned by Pax and 
Knuth ( Primulaceae , in Engler’s Pflanzenreich, 22 (1905), p. 50). 
3 Oest. bol. Zeit. (1875), p. 79. 4 Phytologist, 1 (1844), p. 996. 
6 Trans. Essex Field Club, 3 (1884), pp. 204—205, and Journ. Linn. Soc., 
Bot. 33 (1897), pp. 193-197. 
6 See Journ. of Ecology (1922), pp. 209—210. 
7 The number of plants existing in Britain of another hybrid noticed 
hereafter (namely, P. veris x vulgaris ) is probably actually greater, as this 
occurs all over the country, but the number of plants to be met with at any 
one spot is always small (see post, p. 299). 
