AUTOGAMY BY MOVEMENTS OF STAMENS. 341 



are placed just in front of the approach to the nectaries of the ovary and in such a 

 position are certain to be brushed by insects, whilst no honey is to be found behind 

 the anthers of the three shorter stamens, and insects, therefore, make no attempt to 

 enter past them. These anthers, consequently, retain their pollen, and when the 

 flower is nearly over yield it up for the purpose of autogamy. 



A curious contrivance is exhibited by Aj^hyllanthes Monspeliensis, a plant 

 indigenous to Southern Europe. Like the Star of Bethlehem, it has three long and 

 three short erect stamens in each flower, and the anthers are not at first in contact 

 with the stigma. But before the final closing of the perianth all the stamens slope 

 towards the stigma, which is subdivided into six lobes, three at the top and three 

 lower down, so that the pollen of the three shorter stamens is deposited on the lower 

 stigmatic lobes, and soon afterwards that of the three longer stamens is deposited 

 •on the three upper stigmatic lobes. 



In many plants where all the stamens are of the same length, and where the 

 anthers are already on the same level as the stigma at the time when the flower 

 opens, the process of autogamy is essentially identical with that above described. 

 The anthers are held by erect filaments at a little distance from the stigma, but 

 later on, after various movements have been accomplished by the filaments, they 

 adhere to the stigma and deposit their pollen upon it. This is the case, for instance, 

 in Paris quadrifolia, in several species of Scilla, in Chelidonium and Roevieria, in 

 ■Samolus Valerandi, in Androsace elongata, A. 7)iaxima and A. septentrionalis, in 

 Lysimachia nemorum and in Swertia perennis and S. punctata. It is not possible 

 here to discuss all these plants individually, and only a few points in connection 

 with them will be referred to. In the Herb Paris (Paris quadrifolia) the period 

 during which each flower remains open is very long. The stiff" stamens at first 

 stand out radially, but later they describe an angle of 80° towards the middle of 

 the flower, where they converge over the pistil and press their anthers upon the 

 stigmas. In the plants of the order Primulaceae — viz. Samolus Valerandi, Androsace 

 ■elongata, A. maxima, and A. septentrionalis — the corolla is salver-shaped, and the 

 short filaments, which are adnate to the tube of the corolla, only need to incline 

 slightly towards the axis in order to transfer their pollen to the stigma in the 

 same flower. The majority of these plants are protogynous; the flowers of Swertia 

 perennis and S. punctata alone are markedly protandrous. There is, therefore, in 

 the case of the latter no chance of cross-fertilization at the beginning of the period 

 •of flowering, the stigma being still closed. On the other hand, pollen is available for 

 transport by insects to flowers that happen to be at a later stage of development. 

 The next step is for the stigma to open and so dispose its two lobes that flies 

 arriving with a supply of pollen from younger blossoms are obliged to eflfect cross- 

 fertilization. To prevent restriction or frustration of this process of heterogamy, 

 and also to ensure the preservation of some pollen for autogamy in the opposite 

 •case of an absence of insect-visitors, the five stamens bend outwards simultaneously 

 with the opening of the stigma, exserting their anthers and hiding them under the 

 stellately-expanded petals. If no insects come, and cross-fertilization is therefore 



