384 THE FERTILISATION OF FLOWERS. [PART my 
androus, the style being long and exserted, and the anthers standing 
in the mouth of the long tube (665). ; 
Darwin compared the productiveness of legitimate and illegi- 
timate crossings in Primula veris, P. elatior, Jacq., P. vulgaris, J 
sinensis; Hildebrand in P. sinensis and P. Auricula; Scott in P. 
sikkimensis, P. cortusioides, P. involucrata, and P. farinosa (167). 
According to Darwin, the common Oxlip is a natural hybrid 
between the primrose and cowslip, while the Bardfield Oxlig 
(P. elatior, Jacq.) is a good (heterostyled) species (161, 167). — 
288. PRIMULA ELATIOR, Jacq.—Honey is secreted by the base 
of the ovary. In the short-styled flowers the tube is 15 to 17 mm 
long, and begins to widen at a height of 12 to 13 mm.; the stig 
stands in the middle of the tube and the anthers in the wid 
entrance. In the long-styled form the tube is 12 to 14 mm. long. 
and begins to widen out at a height of 4 to 5 mm.; in the middle 
of the tube, at the base of the expanded portion stand the 
anthers, and the stigma stands at or a little above the mouth o! 
the tube. Humble-bees can insert their heads (5 mm. long) 
wholly into the tube, and so require a proboscis at least 12 mm. 
long to extract the honey from the longest flowers, and one at 
least 7 mm. long to do so in the shortest. As in Pulmonaria 
the bee, if it gains the honey in the ordinary manner and not bh 
biting a hole through the tube, must touch the organs whicl 
stand in the mouth of the flower with its head, and those in the 
middle of the tube with its maxille; and so, passing from flower te 
flower, it effects legitimate cross-fertilisation. Pollen-collecting bee: 
are only able to secure their pollen in the short-styled flowers; 
they learn to recognise the long-styled plants at a distance anc 
to avoid them, and then never perform cross-fertilisation but very) 
often self-fertilisation. 
Visitors : A. Hymenoptera—A pide : (1) Bombus hortorum, L. 2 § (18—21), 
sucking normally, s. and c¢.p., very ab. ; (2) B. silvarum, L. 9 (12—14), sucking 
normally ; (3) B. lapidarius, L. 9 (12—14), do. ; (4) B. confusus, Schenck, 9 
(12—14), do. ; (5) B. terrestris, L. (7—9), makes a hole in the corolla-tube, 
little above the calyx, sometimes biting it with its mandibles, sometimes 
piercing it with its maxille, and so reaching the honey with its tongue (I have - 
sometimes seen this bee, before boring the flower, make several attempts t 
reach the honey in the legitimate way,—-this observation is of interest, ¢ 
proving that the bee is not guided by instinct to the plant adapted for it, but 
that it makes experiments, and gets its honey where and how it can) ; (6) Osmia 
rufa, L. ¢@ (7—8); (7) Apis mellifica, L. $, I saw both of these species 
thrust their tongues into several flowers, and then abandon the plant ; (8) 
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