THE FERTILISATION OF CERTAIN PLANTS. 
47 
in its exit from the flower does not touch the stigma, and so 
fertilise the flower with its own pollen. The bee is so large 
comparatively, and so abrupt in its departure, that though I 
watched repeatedly, I was unable positively to assure myself on 
this point. But it appeared to me that it did not, and I fancy 
that the projecting point below the stigma serves as a safeguard 
against this ( a , fig. 1 ). At any rate, it is easy to convince one- 
self by watching that not all the pollen is left on the stigma of 
the same flower, but that much is carried off to other blossoms. 
Moreover, when the bee leaves a flower, the stigma is already 
occupied with the foreign pollen which the insect left there in 
entering, and there is, consequently, little or no exposure of 
viscid surface to which the fresh pollen may adhere. 
The structure of yellow cow wheat ( Melampyrum ) (fig. 2) 
so closely resembles that of red rattle that I need not describe 
it in detail. Here also the opposite anthers form one common 
receptacle, which is kept closed till a bee opens it by dilating 
the hood. There are some small differences to suit the arrange- 
ment to the somewhat different form and position of the flower, 
which is set horizontally, and not erect as in red rattle, but the 
main features are the same.* One little point is, however, 
worth noticing, and that is that the narrow hood fissure through 
which the insect must pass its head is made narrower still by 
the filaments of the front pair of stamens. The insect’s head 
passes between these, pushing them asunder, and thus the 
dilating force acts still more directly on the opposing anthers 
than is the case with the other flower. 
The cow wheat is fertilised by the small buff-bodied humble 
bee. The large humble bees also visit the flower, but apparently 
the fissure is too small for their heads, for they adopt the 
common treacherous habit of bees when they are unable to get 
in at the mouth, and make a hole in the tube just above the 
nectary, and so reach the secretion. The very small calyx 
admits of this robbery, whereas in red rattle the large leafy 
calyx acts as a safeguard. 
What practised thieves these large bees are, is plain from the 
fact that, on gathering 100 open blossoms, I found the hole in 96, 
only 4 being intact. It occurred to me that I might use this 
habit of the bees to throw light on a point of some little in- 
terest, the period, namely, at which a flower begins to secrete its 
nectar. If there be nectar in the tube before the flower opens, 
* In order that the pollen may escape and fall upon the bee, the fissure 
between the opposing anther cells must occur at their lowest part. This, in 
the erect Pedicularis, is on the side turned towards the tube ; in the hori- 
zontal cow wheat, on the side turned towards the inferior lip. In each case 
the fissure occurs where it is required. 
