PART IIL. | THE MECHANISMS OF FLOWERS. 251 
Visitors: A. Hymenoptera—Apidew: (1) Bombus terrestris, L. 2, freq. ; 
(2) B. pratorum, L. ? (in Stromberg), very ab. ; (3) B. Scrimshiranus, K. 9 ; 
_ (4) Apis mellifica, L. $, very ab. ; (5) Andrena nitida, K. ¢, all sucking ; 
| (6) A. albicans, K. ¢ 2; (7) A. Gwynana, K. ¢ 9; (8) A. fulva, Schrank, 
_ 9, the last three both s. and f.p.; (9) Halictus rubicundus, Chr. 9,s._ B. 
Diptera—(a) Muscide: (10) Scatophaga stercoraria, L., s. ; (11) Calliphora 
erythrocephala, Mgn., s. ; (b) Syrphide: (12) Eristalis eneus, L., s. and f.p. ; 
(13) Syritta pipiens, L., do. The insect-visitors cause cross-fertilisation in the 
same way asin R. nigrum. See also No. 590, I. 
_ — 
Ribes sanguineum, Pursh.—The calyx-tube is 3 mm. deep; the 
erect petals form a tube more than 5 mm. deep. As a rule, there- 
fore, the honey is obtained and the Rowers fertilised by bees only, 
especially the hive-bee. 
ftibes aurewm, Pursh—The calyx-tube is 10 to 11 mm. deep, 
and the erect petals add 3 mm. more to its depth. The honey is 
only accessible to very long-tongued bees, and the flowers have been 
found by Delpino in Italy and by me in Lippstadt to be visited 
only by Anthophora pilipes, 2? , whose proboscis is the longest among 
our native bees (20 mm.). In the two last species the flowers 
persist a long time after the reproductive organs are withered, and 
even become more conspicuous, since the petals in 2. sanguinewm 
change from white to pink, and those of &. awrewm from bright 
yellow to carmine. By this peculiarity, not only is the power of 
attracting insects increased, but the more intelligent fertilising 
_ agents are told at the first glance which flowers contain no more 
. treasure for them, the result being that they visit and fertilise more 
_ flowers in the same time (590, I.). The same kind of colour-change 
/ occurs in several species of Fuchsia and Lantana, in Diervilla 
(Weigelia) rosea, Melampyrum pratense, L., Fumaria capreolata, var. 
| pallidiflora, Jord., and others (575). 
= kttbes petreum, Wulf., is, according to Ricca, slightly pro- 
terogynous (665); according to my own observations it is 
_ homogamic (609). 
Hk cera LE LOE TE EET GP DO NAO A Fa 
Orv. CRASSULACE Z. 
Bryophyllum calycinum, Salisb., is proterandrous, and has hang- 
g, tubular flowers, rich in honey. Delpino supposes humming-birds 
be the fertilisers, despite the pale greenish colour (177). 
4 162. SepuM AcRE, L.—Although the plant is small, it is 
i endered conspicuous on the bare spots where it grows by its 
