112 THE FERTILISATION OF FLOWERS. [PART II. : 
other two drops of honey can be reached without touching the 
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stigma, and seem to afford no aid in fertilisation. In default — 
of insect-visits the upper part of each of the long anthers bends 
back so far’as to touch the stigma, thus effecting self-fertilisation. 
This self-fertilisation is probably efficient: at least B. rapa, L., 
was found by Hildebrand to produce seed when self-fertilised (351). 
In sunny weather I have always found the honey very evident. 
Sachs,! who says “the dark-green nectaries lying between the 
stamens of Brassica retain their secretion within them,’ has 
probably examined the flowers in dull weather. 
Visitors: A. Coleoptera—Nitidulide : (1) Meligethes, very ab., feeding on 
the petals and on pollen. B. Hymenoptera—Apide : (2) Andrena nigroznea, 
K. 9,s.; (8) A. Gwynana, K. 9, s. and fip.; (4) A. fulvicrus, K. 9, cp. ; 
(5) A. nana, K.?,s. and f.p. ; (6) Halictus cylindricus, K. 9 ; (7) Apis mellifica, 
L. $,s.andf.p. (I did not see the hive-bee preserve any definite order in 
visiting flowers of this plant ; frequently a bee after visiting a second flower — 
returned to the first). C. Thysanoptera—(8) Thrips, ab. 
40. SINAPIS ARVENSIS, L—The honey-glands are placed as 
in Brassica. When the calyx expands, the glands are visible and 
accessible from the outside, and insects can reach them without 
touching the essential organs of the flower. The close aggregation 
of the flowers however renders it more convenient for the insect 
to thrust its proboscis down between the stamens, and in point 
of fact I have never seen an insect visitor obtain the honey from 
the outside. The twisting of the stamens and the likelihood of 
cross-fertilisation are as in Cardamine pratensis; as the flowers 
wither, however, the anthers turn their pollen-covered sides up- 
wards, and finally their tips bend downwards, so that they effect 
self-fertilisation if their pollen has not already been removed. 
Visitors : A. Diptera—Syrphide : (1) Eristalis eneus, Pz.; (2) E. arbus- 
torum, L. ; (3) Rhingia rostrata, L., all these both s. and fp. B. Hymen- 
optera—(a) Tenthredinide : (4) Cephus spinipes, Pz., and several small sp. 
in great abundance, lh. and f.p.; (b) Apidew: (5) Halictus leucozonius, 
Schrk. 9, ¢.p.; (6) Andrena nana, K. ¢,s.; (7) Apis mellifica, L. $, very 
ab., both s, and c.p. (I found it collecting pollen on Sinapis on Oct. 2, 1869). 
©. Coleoptera—(8) Coccinella Tpunctata, L., lh, D. Lepidoptera—(9) 
Euclidia glyphica, L., s. See also §90, IL. 
A variety of Sinapis arvensis bears cleistogamic flowers at St. 
Croix, where the temperature is 25° C. (762). 
1 Lehrbuch der Botanik, 2nd ed., p. 110. 
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