362 AUTOGAMY. 



tion in the mouth of the corolla, which necessitates contact between the receptive 

 tissue at their tips and the bodies of the humble or hive bees, which find their way 

 to the flower in search of honey. If these insect- visitors bring with them pollen 

 from other flowers, cross-fertilization is inevitable. As they push lower down into 

 the flower, the bees receive an additional load of pollen from the stylar column, the 

 surface of which is coated with it, and this new store they may convey to other 

 blossoms. When the time for the flower to fade is near at hand, the style-arms 

 become revolute, and press the receptive tissue of their tips upon the stylar column, 

 taking from it a coating of pollen, of which there is still a sufficient quantity cling- 

 ing to the surface (see fig. 302 9 ). The large-flowered Campanula persicifolia has 

 been selected as a type of these Bell-flowers. The style-arms in this species are 

 from 1 cm. to 1*6 cm. long, and they coil into spirals of from 1^ to 2 involutions. 

 In most of the other Bell-flowers (e.g. C. barbata, C. carpatica, C. pyramidalis, G. 

 Rapunculus, C. spicata) the revolute style-branches have only from 1 to 1 coils in 

 each spiral, whilst in some few (e.g. C. patula, C. rapunculoides) there are rather 

 more than 2 complete coils in each. The Rampion genus (Phyteuma), here exempli- 

 fied by Phyteuma orbiculare (see figs. 302 10 and 302 n ), differs from the Bell-flowers, 

 which are its nearest allies, in the circumstance that the deposition of pollen and 

 retraction of the emptied anthers occurs at a time when the tips of the petals are 

 still connate into a tube. For a short time the end of the stylar column may be 

 seen covered with pollen projecting beyond the corolla, and in this position the two 

 arms disunite and expose their stigmatic tips to pollination by insects (see fig. 302 10 ). 

 If no insects visit the flower the style-branches roll back and bring their tips into 

 contact with the pollen on the stylar column (see fig. 302 n ). In all the species that 

 have been examined (Phyteuma confusum, P. hemisphcericum, P. Halleri, P. 

 orbiculare, P. spicatum) the style-branches are wound into from 1 to 2 complete 

 coils. In the case of Phyteuma Halleri the further observation was made, that 

 after the accomplishment of autogamy the transparent hairs on the stylar column 

 and the pollen adherent to them rapidly dry up, whilst the branches of the style 

 unroll again. 



Of the Gentians, the little Gentiana prostrata, which grows on the mountains 

 in the vicinity of the Brenner Pass in Tyrol, affords a striking example of the 

 phenomenon in question. The flowers are protandrous; the anthers in the bud are 

 contiguous to the short style and closed stigma, and, when they open, their pollen 

 is deposited upon those organs. Upon the expansion of the corolla, the pollen is 

 available for other flowers through the agency of insects. Somewhat later the 

 stigmatic lobes part, and if after this insects visit the flower, they brush against the 

 receptive spots of the stigma, and may dust them with extraneous pollen. Lastly, 

 the two stigmatic lobes curl back until the receptive tissue upon their upper sur- 

 faces reaches the residue of pollen still sticking to the short style. 



Much less common modes of operation are for the revolute stigmas to take the 

 pollen from the edge of the tube of connate anthers, from hairs on the corolla, from 

 bristles on the pappus, or from depressions in the petals. The case of abstraction 



