AUTOGAMY BY BEXDIXG OF STA:MEXS. 337 



the approach to the floral receptacle open. Dehiscence has already taken place in 

 the case of the anthers of the stamens inserted in front of the sepals, and their 

 pollen is available for cross-fertilization by means of insects, but not for auto- 

 gamy, owiag to the fact that the receptive tissue of the style in the same flower 

 is stiU inaccessible. (2) The anthers of the stamens inserted in front of the 

 sepals drop off, or else their filaments become reflexed and are exserted beyond 

 the periphery of the flower. The styles move asunder and arrange themselves 

 like the spokes of a wheel in the middle of the flower, where they are Kable to 

 be covered with pollen brought by insects from other blossoms. The anthers 

 of the stamens inserted in front of the petals are stiU closed. (3) Owing to a 

 growth of the erect filaments of the last-mentioned stamens, their anthers are 

 brought to the same height as and in direct contact with the spreading stigmas. 

 Dehiscence ensues, and the liberated pollen is deposited on the receptive stigmatic 

 tissue. In annual caryophyllaceous plants — e.g. in Silene conica — the whole pro- 

 cess takes place ia the course of a single day, whereas in the perennial Bianthus 

 glacicdis it occupies five or six days, or, if the weather is bad, from seven to nine 

 days. 



One of the commonest contrivances for effecting autogamy is the following. 

 Anthers and stigmas stand at the same height, though, owing to the position and 

 direction of the filaments, the anthers are so far from the stigma that no transfer- 

 ence of the adhesive pollen to it can take place. At the proper moment, however, 

 the straight and rigid filiform filaments perform certain special movements with the 

 object of conveying pollen from the anthers to the stigma in the same flower. The 

 filaments incline themselves towards the centre of the flower, bringing the anthers 

 into contact with the stigma there situated and pressing the poUen issuing from 

 their loculi on to the receptive tissue. In some plants belonging to this category 

 the displacement of the stamens, which is like the motion of the hands of a clock, is 

 preceded by an elongation of the filaments, and in this respect the plants in question 

 form a transition from those previously described, in the flowers of which autogamj- 

 is due to the growth of the filaments. As instances of these transitional forms may 

 be mentioned Azalea procumbens, Draba aizoides, HaplophylluTti Biebersteinii, the 

 numerous Saxifrages comprised in the groups of Aizoonia and Tridactyhtes, and 

 more particularly many Alsinese and other Caryophyllaceae. The Saxifrages exhibit 

 a number of individual peculiarities into which we cannot enter in any detail. We 

 must content ourselves with describing two species as representatives of the two 

 groups above referred to, and will select for the purpose Saxifraga Burseriana, a 

 plant which grows in the eastern Dolomites, and flowers in early spring, and Saxi- 

 fraga controversa of the group Tridactylites. The flowers of Saxifraga Burseriana 

 are protogynous, and the two spreading stigmas are already susceptible of pollina- 

 tion at the time when the petals are only just open, and the anthers are still closed 

 and held near the bottom of the flower on quite short filaments. During this first 

 period of flowering the blossom is adapted to cross-fertilization. Soon afterwards 



the stamens in front of the sepals lengthen in definite succession, and the anthers, 

 Vol. II. 72 



