S44 AUTOGAMY. 



on the roiigh surface of the pad of tissue in the middle of, the flower ceases, the 

 pollinated stigmas turn brown, and the period of bloom, for that particular flower 

 comes to an end. The imperfect staminiferous flowers do not unfold until all the 

 hermaphrodite flowers are over, a fact which can only be interpreted as indicating 

 that their pollen is to be devoted to the fertilization of protogynous hermaphrodite 

 flowers of other individuals which are still in the first stage of flowering. Fool's 

 Parsley {jEthusa Gynapiwm, see figs. 296 '•*'^) difiers from the Venus' Comb and 

 the other annual Umbellifers above referred to in that all the flowers of an umbel 

 are hermaphrodite, and that the filaments, which in the bud are tucked in like 

 springs (fig. 296^), not only straighten out when the flower opens, but elongate, 

 and thus raise the anthers to a higher level than the stigma. Also in Fool's Parsley, 

 ,as has been mentioned before, the anthers are not laid right against the stigmas, 

 but remain a little higher, and let their pollen fall upon them from above (see 

 iig. 296^). This at least is what I saw in the case of the common Fool's Parsley or 

 jEthusa Gynapium; the small JEthVjSa segetalis, on the other hand, according to 

 my observation, much more frequently brings its anthers into contact with the 

 stigmas in the same manner as the Venus' Comb (see fig. 296 *). 



Autogamy of the same type as that described in the above instances of annual 

 Umbelliferse also takes place in many small-flowered Bed-straws (e.g. Galium infes- 

 ■tum, G. Mollugo, G. tricorne), in the Dodder (Guscuta), in the Alpine Enchanter's 

 Nightshade (Gircwa alpina), and in Agrimony (Agrimonia Eupatoria). Of the 

 Enchanter's Nightshade (see figs. 297 1'^-^-*), it is only needful to note that the 

 number of stamens is limited to two, and that sometimes one anther alone is laid 

 upon the stigma (297 % but not infrequently both subserve the purpose of auto- 

 gamy in that manner (297*). In the latter case the stigma looks as if it were 

 grasped by the two limbs of a pair of tongs. The flowers of Agrimony have from 

 12 to 20 stamens, and are protogynous. The anther-fiOlaments are very slightly 

 incurved, each corresponding to about a sixth part of the circumference of a circle 

 (fig. 297'^), but as soon as dehiscence takes place the filaments bend one after 

 another towards the centre of the flower (see fig. 297 ^) until they are in the form 

 of semicircles, and some of the anthers covered with pollen come into direct contact 

 with the stigmas, which are still in a receptive condition (fig. 297 ^). Soon after the 

 ■stigmas have thus been furnished with pollen the anthers drop off the filaments, 

 ^nd the latter coil up still more as is shown in fig. 297 ^'^. 



Several species of Stonecrop (e.g. Sedum annuum, S. atratum, S. dasyphyllum), 

 ^nd some House-leeks (e.g. Sempervivum montanum, S. Ruthenicum) have two 

 kinds of stamens in each flower, namely, those inserted in front of the sepals and 

 those inserted opposite the petals. The anthers of the former are the first to open, 

 and as they are quite close to the stigmas only a slight inclination of the curved 

 filament is necessary to bring about autogamy. After a deposition of pollen upon 

 the stigmas has already taken place, the filaments opposite the petals also curve 

 over inwards, and the anthers, which meantime have undergone dehiscence, are 

 held right over the stigmas. But, seeing that the latter are by this time withered 



