362 



ANGIOSPERMAEDICO TYLEDONES 



stronger than that of female ones. The young branches are of a rather brig! 

 ochre-yellow, which gives the plant a certain conspiicuousness ; the large, thic 

 internode below the small inflorescence may be considered as an excellent extra-flor 

 device to attract attention. 



Kirchner (Jahreshefte Ver. Natk. Stuttgart, xlix, 1893, p. 104) confirms Lind^ 

 man's observations regarding the fragrance. He says that both male and female 

 flowers clearly secrete nectar, the male ones usually less than the female, the lattCHl 

 being sometimes full up to the tips of the perianth lobes. These in the male flowel' 

 at the beginning of anthesis are so upright that the brittle pollen bursting from its 

 receptacles bars the way to the base of the blossom, and must therefore adhere to the 

 proboscis of an insect probing for nectar. In the course of anthesis the perianth;; 

 lobes diverge more widely. 



Visitors. The following were recorded by the observers stated. 



Kirchner, the honey-bee, only visiting the male stocks, and leaving alone the 

 smaller, feebly odorous, female flowers, which of course yield no pollen. PoUination 

 is effected by flies (Pollenia rudis F., freq. ; P. vespillo F., do. ; Spilogaster duplicata 

 Mg., less freq.) which visit flowers of both kinds. Bonnier saw the honey-bee. 



th.' I 



I 



XCVI. ORDER .S-^iVr^Z^C^^^ R.BR. 



781. Thesium L. 



Flowers homogamous with concealed nectar secreted at the base of the coroll 

 tube. Kerner ('Nat. Hist. PI.,' Eng. Ed. i, II, p. 125) says that the anthers whic 

 have dehisced in dry weather close up again when it is damp. Heterostyly som^ 

 times occurs. 



2516. T. alpinum L. (Herm. Miiller, ' Alpenblumen,' pp. 206-7 ; Schul 

 Beitrage,' II, p. 161; Kemer, loc. cit. ; Ewart, Ann. Bot., Oxford, vi, 1892, 



pp. 271-90.) The corolla 

 tube of the homogamous 

 flowers of this species is only 

 2 mm. deep. When visited 

 by insects, cross-pollination is 

 favoured (according to Her- 

 mann-Miiller), as anthers and 

 stigma come into contact with 

 opposite sides of the insects' 

 bodies. Should such visits fail, 

 automatic self-pollination takes 

 place towards the end of an- 

 thesis when the flower closes, 

 by contact of anthers and 

 stigma. Schulz says that this 

 is less easily effected in plants in the Riesengebirge. 



Kerner states that the anthers, after having been pollinated, close up in half 

 a minute. The walls of the anthers are rendered damp by means of a characteristic 

 tuft of hairs growing on the perianth, which Kerner describes as follows :- 



Fig. 360. Thesium alpinum, L. (after Herm. Mailer). A 

 Flower seen from above. B. Do., in longitudinal section (x 13). 

 , nectary ; shy nectar receptacle ; si, stigma. 



i 



