PART II. | THE MECHANISMS OF FLOWERS. 193 
--and so all the flowers were still unfertilised. The bees flew 
humming from one flower to another, clung by their legs to the 
alee, and thrust their heads with outstretched proboscis beneath 
the vexillum while the abdomen hung down. While the head 
and its proboscis were thus placed just as if they were sucking 
honey from the base of the flower, the midlegs were in active 
movement, scraping pollen into the baskets on the hindlegs. On 
May 14, 1871, I again watched the hive-bee at work, when most 
_of the flowers had now exploded. A single bee flew on to ten or 
twenty plants, whose flowers had all been fertilised, without 
stopping on any flower. At last it found a young unfertilised 
flower, on which it eagerly descended. This long search and 
occasional descent upon young unfertilised flowers was frequently 
_ repeated ; but sometimes I saw a bee, after seeking in vain for 
_ young flowers, settle on an old exploded one, and insert its pro- 
boscis as if the flower contained honey. Sometimes also I saw a 
hive-bee visit a young flower without causing it to explode. 
Besides the hive-bee, I have only seen Andrena fulvicrus, 
_ K. ?, A. nigro-aénea, K. 2, and Halictus cylindricus, F. 2, collecting 
_ pollen on this plant, all very frequently. 
110. Genista pILosa, L.—The mechanism of this flower is like 
that of G. anglica. It has been thoroughly described by Delpino, 
_ who found the plant sterile to its own pollen (178, 360). I have 
only seen the honey-bee collecting pollen on it. 
- 111. Cytisus Lasurnum, L.—In the flowers of Cytisus La- 
} burnum, as in those of Melilotus and Trifolium, the reproductive 
organs simply emerge from the carina and return within it. The 
connection of the ale with the carina is not a firm one, being 
formed simply by a shallow bulging depression in each ala (e, 1) 
which fits into a corresponding depression on the side of the 
carina ; yet this is quite sufficient, as a slight pressure suffices to 
epress the ale and carina. The elasticity of the carina is small ; 
| it is sufficient to bring the carina back to its original place after 
repeated slight depressions, but not sufficient if the carina be 
| pressed far down. Accordingly, after repeated visits of humble- 
| bees the essential organs protrude freely from the slit. 
| The flowers are characterised by a peculiar kind of proteran- 
 drous dichogamy. Immediately before the bud expands, the stigma 
} lies in the apex of the carina surrounded by transparent, stiff, erect 
| ib hairs ; these overtop the stigma, and in the young flower they 
O 
