AUTOGAMY BY THE BENDING OF THE PISTIL. 353; 



sible. Thus, dichogamy, involving hardly half-an-hour's interval between the 

 attainment of maturity in stigmas and anthers respectively, is suflScient to ensure 

 cross-fertilization at the commencement of the period of bloom in each flower of 

 this kind of night-flowering plant. A further adaptation with a view to hetero- 

 gamy is shown in the position of the stigma in front of the anther in the first stage 

 of floral development (see fig. 299'). On the intrusion of insects— Sphingidse,. 

 Noctuse, &c. — into the interior of the flower the large stigma is the first object 

 encountered, and next to it come the anthers, and there is therefore a possibility 

 that even during the time that the anthers are open and have their pollen exposed 

 cross-fertilization may take place through the agency of insects. If, however, no- 

 insects visit the flower the style bends down the very next morning in an open 

 curve and lays the stigma flat upon the anthers (see fig. 299 *). The pollen readily 

 adheres to the surface of the stigma, as may be seen by removing that organ after 

 it has become appressed to the anthers, when a thick layer of pollen will be found 

 sticking to it (fig. 299 % 



Inflections of the style in all respects similar to those exhibited in Morina occur 

 in the flowers of numerous Rhinanthacese, e.g. in Rhinanthiis irdnor, Trixago 

 apula, Mdampyrum pratense, Euphrasia Tninima (see figs. 299 * and 299 '). In 

 these plants we find, in general, a repetition of the entire process above described, 

 except for the circumstance that the pollen is not adhesive but mealy, and is not 

 transferred to the receptive tissue by appression of the stigma to the anthers — it 

 being sufficient to place the stigma under the anthers by means of an inflection of 

 the style. The stamens in this case are of the sugar-tongs type (c/. p. 271). In 

 the first and second stages of floral development the mealy poUen only falls out of 

 the anthers on the occasions when the stiff" filaments of the stamens are forced apart 

 by insects. Should no insects visit the flower the pollen remains in the loculi. In 

 the third stage of flowering the filaments become flaccid, as does also the portion of 

 the corolla adjacent to them, and in consequence the anthers, which have hitherto 

 been closely coherent, move a little apart from one another and let the pollen fall 

 out. Meanwhile the style has bent down sufficiently to bring the viscid stigma 

 under the front pair of anthers, so that a portion of the pollen is caught upon its 

 glistening surface, with the result that autogamy is effected (see fig. 299 ^). It is 

 not uncommon for the inflection of the upper third of the style to be so strong as 

 to amount to an involution, and the stigma is then pushed between the disuniting^ 

 anthers and comes into contact with the hairs which clothe the anthers, and which 

 are usually powdered all over with pollen. 



Tricyrtes, Morina, and the Rhinanthacese just mentioned, are all protogynous, 

 whilst on the other hand, the Evening-primrose, Willow-herb, Campion, and Mal- 

 low, in which autogamy likewise occurs in consequence of the style bending down 

 to the anthers, are protandrous. When the petals of the Evening-primrose {(Eno- 

 thera biennis, (E. muricata, kc), or of the large-flowered species of Willow-herb 

 (Epilobium hirsutum, E. angustifolivmi, see fig. 300) expand, the four branches of 

 the style, which bear the receptive tissue and constitute the stigmas, are closely 



Vol. II. 73 



