“parr ut] THE MECHANISMS OF FLOWERS. 1 
stamens undergo no twisting, but in sunny weather they bend 
backwards as far as the nearly upright sepals permit them. As 
to the likelihood of cross- or self-fertilisation, the same holds as 
in the case of Nasturtium silvestre. When in rainy weather the 
flowers do not fully open, or when they close up again without 
4 being visited by insects, self-fertilisation occurs. 
Visitors: A. Diptera—(a) Leni : (1) Argyromeeba aca Fallen ; 
(bd) em (2) Eristalis pide be .; (3) E. nemorum, L. ; (4) E. sepul- 
eralis, L. ; (5) Helophilus floreus, L. ; (6) Syritta pipiens, L., very ab. 3 ; (7) 
Melithreptus teeniatus, Mgn. ; (8) ‘Aéeia podagrica, F., very abe ; (9) Pipiza 
chalybeata, Mgn., all these Syrphide now s., now fp. ; (c) Muscide : (10) 
Siphona cristata, F. B. Hymenoptera—(a) Ichneumonide : stragglers; (b) 
Sphegide: (11) Oxybelus bellus, Dib., ab. ; (12) O. uniglumis, L., very ab. ; 
(18) Cemonus unicolor, F.; (14) Cerceris variabilis, Schrk., very ab.; (c) 
 Uhryside : (15) Hedychrum lucidulum, F. ¢; (7) Apide: (16) Prosopis com- 
"munis, Nyl. ¢ 2, very ab., s. and f.p.; (17) P. armillata, Nyl. ¢ 9, do. ; (18) 
if Halictus nitidiuseulus, K.9, 5. ; (19) H. lucidulus, Schck. 2, s.; (20) Andrena 
- parvula, K.? ; (21) A. pilipes, F.¢,s. C. Coleoptera—(a) Dermestide -: (22) 
_ Anthrenus pimpinelle, F.; (b) Malacodermata: (23) Dasytes flavipes, F. ; 
(24) Anthocomus fasciatus, F, ; (25) Malachius bipustulatus, F., gnawing the 
anthers and petals. D, Lepidoptera—(26) Sesia tipuliformis, L., s., frequent. 
Hutchinsia alpina, R. Br., is proterogynous with persistent 
stigmas. It is visited and cross-fertilised by Diptera (609). 
39. BRASSICA OLERACEA, L.—Two honey-glands lie on the 
inner side of the bases of the two short stamens, and two others 
occupy the position of the aborted pair, 7.c. are antero-posterior. 
| a honey-drops secreted by the two former distribute themselves 
ach between a short stamen, the two adjacent long ones, and the 
; F nistil and are easily visible on looking straight downwards into 
F in. open flower; the drops from the other pair of glands lie 
ctside eticen the two adjacent long stamens, and these drops 
increase until they sometimes reach the sepals. The two shorter 
Manithers stand sometimes on a level with the stigma, usually 
: 4 owever they are not so high; they curve outwards, but their 
?P ollen-covered sides face the centre of the flower. The long 
- stamens perform a quarter- or half-revolution without increasing 
| their distance from the centre of the flower, so that the pollen- 
covered sides of their anthers are either turned towards the 
neighbouring short stamen, or else directly outwards. An insect 
in sucking the honey at the base of a short stamen touches with 
one side of its head or proboscis the stigma, and with the other 
_ a short stamen and usually a long one at the same time: the 
2. 
