SANTALACEAE 363 



' The anthers of the Bastard Toad-flax {Thesium alpinum) shut up within thirty 

 seconds of their being moistened. In this plant the process of closing is rendered 

 additionally interesting by the fact that the moistening of the anther-walls is effected 

 by peculiar tufts of hair projecting from the perianth. . . . The open flower of Thestum 

 has the limb of its perianth turned to the sky. The position is maintained unchanged 

 day and night, and even the occurrence of bad weather does not cause any alteration 

 in the direction of the flower-stalks or the position of the flowers. Hence rain-drops 

 falling from above and the dew formed on clear nights must inevitably rest on the 

 open flowers. The immediate wetting of the entire flower is, however, prevented by 

 peculiarities in the form of the limb. The anthers close with great celerity upon the 

 deposition of the drops, the explanation being that the perianth lobes are connected 

 with the anthers standing in front of them by a bunch of twisted hairs, which not only 

 are themselves peculiarly susceptible of being wetted, but conduct the water to the 

 anthers and so cause the anther-walls to close/ 



These hairs have been anatomically examined by Miss M. F. Ewart, who 

 distinguishes between two kinds : 



(i) Short, thick hairs, directed downwards towards the base of the style. 



(2) Long, thin ones, directed upwards towards the anthers. 



The former are situated on each side of the anthers and spring from the inner 

 surface of the perianth ; the others stand behind each anther. Both kinds secrete 

 resin, which often fastens the longer hairs to the anthers. Many species also possess 

 long threads hanging from the perianth leaves. 



Two groups connected by transitions may be distinguished : 



(i) Species, such as T. spicatum and T. capituliflorum, possessing short, down- 

 wardly directed hairs at each side of the anthers and long threads hanging from the 

 perianth. The style in these species is short and the perianth lobes much thickened. 



(2) Species, such as T. debile and T. paniculatum, possessing long, upwardly 

 directed hairs situated behind the anthers and the short or small threads on the 

 perianth. The style is long and the perianth lobes scarcely thickened. 



Miss Ewart says that the hair-tufts on flowers of the first group probably serve 

 to hold the pollen firmly by means of the excreted resin, while the hanging threads 

 guide the insect visitor to the deeply situated stigma. 



In flowers of the second group these threads are not necessary, on account of 

 the length of the style. The threads situated behind the anthers do not serve (in 

 Miss Ewart's opinion) as supports for them, but probably prevent the insect probing 

 for nectar from diverging from the right way, and also hold back the pollen close to 

 the flower-entrance. 



Visitors. The following were recorded by the observers, and for the localities 

 stated. 



Schulz (Riesengebirge), 50 Hymenoptera (mostly small), as many flies, and 

 a few small beetles. Herm. Muller (Alps), not a single visitor. MacLeod (Pyrenees), 

 a Muscid (Bot. Jaarb. Dodonaea, Ghent, iii, 1891, p. 440). 



2517. T. intermedium Schrad. (Schulz, ' Beitrage,' II, pp. 161-3.) The 

 flowers of this species are heterostylous and homogamous. In the long-styled form 

 the anthers reach just above the middle of the style, and automatic self-poflination 

 is therefore rendered difficult. In the short-styled form the anthers are situated 



