300 
Miller Christy 
very frequently dig up roots and remove them to their gardens, 
thus causing it to be much less common than it would be otherwise. 
Again, in connection with this hybrid, there is nothing surprising 
in hybrids between the two parent species arising naturally wherever 
the two grow in close proximity, as they often do. It is true that 
their habitats differ somewhat (the Primrose growing mainly in 
woods and hedge-rows: the Cowslip in open meadows 1 ); but Cow¬ 
slips often grow just within the edges of a wood in which Primroses 
grow, or in meadows closely adjoining, and the hybrid is found not 
infrequently in these situations. Moreover, it is known that both the 
parent species are visited by the same species of insect 2 . Thus, as 
stated already 3 , the Brimstone butterfly (Gonepteryx rhamni) has 
been seen to visit both, as also have several large species of bee. 
On 13th April 1914, I watched a small blackish bee (Anthophora 
acervorum) visiting Primroses on the edge of a cut-down wood at 
Roxwell, Essex. After it had visited twenty Primrose flowers, it 
immediately visited two Cowslip flowers growing only two or three 
feet distant and on (or very close to) a spot where, in earlier years, 
I had seen undoubted hybrids growing—an observation very much 
to the point in this connection. 
1 Inasmuch as hybrids are found not uncommonly in both these habitats, 
it seems probable that both plants supply at times the female parent. 
2 See Journ. Linn. Soc., Bot. 46 (1922), pp. 105-139. 
3 See ante p. 298. 
CAMBRIDGE: PRINTED BY J B. PEACE, M.A., AT THE UNIVERSITY PRESS 
