31 1 AUTOGAMY. 



perianth closes for the night, the pollen is transferred from the inner faces of its 

 segments to the stigmas. Two subsidiary circumstances co-operate in bringing 

 about this act of autogamy. The first is, the fact that the free extremities oi' the 

 styles which bear the stigmatic tissue curve outwards when the flower's end 

 approaches, and the second is, the circumstance that the excessive elongation is 

 especially marked in the three perianth-segments which are opposite the stigmas. 



The same events take place in the flowers of the Meadow Saffron (Colchicum 

 autwmnale). Anyone crossing a meadow in the autumn in which this plant is 

 growing may see what a great difference exists between young and old flowers in 

 respect of the length of the perianth-segments, and can easily convince himself of 

 the connection between this diversity and the operation of autogamy as explained 

 above. In the Meadow Saffron the phenomenon is somewhat complicated by the 

 circumstance that heterostylism (see p. 302) plays a much more important part 

 in this instance than in the other Liliaceae. Colchicum possesses long -styled, 

 mid-styled, and short-styled flowers, which all grow promiscuously together in one 

 and the same meadow, and the elongation of the perianth-segments is anything hut 

 uniform in these three forms. Careful measurements of some five hundred specimens 

 gave the following remarkable result. In long-styled flowers the three longer 

 perianth-segments grow 9 mm. and the three shorter 12 6 mm.; in short-styled 

 flowers the longer segments grow 10 mm. and the shorter 15 mm., and in the mid- 

 styled flowers the longer segments grow 135 mm. and the shorter 18'5 mm. I shall 

 return to the subject of heterostylism again presently, and shall then have an oppor- 

 tunity of entering more fully into its significance; at present it is only necessary to 

 mention that the stigmas of the short-styled flowers, when the latter are nearly 

 over, come into contact not only with the pollen sticking to the perianth-segments, 

 but also with the tips of the anthers themselves, for in this form there is a propor- 

 tionate growth of the filaments. 



This same process, which in Colchicum autumnale, in Sternbergias and in Gen- 

 tians of the Ccelanthe tribe only culminates in autogamy after the lapse of a week, 

 is accomplished in the delicate plant Sisyrinchium of the order Iridacese in the 

 course of a few hours. Apart from their ovaries, which are inferior, the flowers 

 of Sisyrinchium are constructed similarly to those of Liliacea?. The three small 

 petaloid stigmas, in which the styles terminate, project above the anthers. The 

 latter are coherent into a tube and open extrorsely, whilst the flower is still in the 

 bud state, and the consequence is that some of their pollen is affixed to the con- 

 tiguous leaves of the perianth. The flower opens out into a cup, and insects may 

 then cause heterogamy; but on the approach of evening the perianth closes again, 

 and autogamy takes place owing to the fact, that in the course of those few hours 

 the petals have lengthened exactly enough to bring the pollen sticking to their inner 

 surfaces to the level of the stigmas. 



Reference must also be made to those Composites in which autogamy is brought 

 about by means of an elongation of the ligulate corolla, and the consequent uplifting 

 of the pollen adherent to it. In most and probably in all species of Crepis, Hiera- 



