AUTOGAMY BY COILING OF STAMENS AND PISTIL. 



357 



brought in the process of involution into contact with the pollen of one or more 

 anthers. Most of the plants which exhibit this curious phenomenon have the 

 common property of being ephemeral, but they belong to most different families. 

 In a number of Commelynacese — Goinmelyna coelestis, for example (see fig. 301) — 

 the stigma is situated in front of and lower than the anthers when the flower, 

 which faces sideways, is quite newly open (fig. 301 ^ ). Honey is secreted on curious 

 palmately-lobed nectaries, and if in this first period of the flower's development 

 insects come in quest of the honey they make use of the anthers to alight on, and 

 in so doing besmear themselves with the pollen, which is already emerging through 

 the lateral sutures of dehiscence of the anthers. Soon afterwards the stamens 

 become spirally coiled, and the style, which meanwhile has grown to the same 

 length as the stamens, curves in such a manner as to bring the stigma to a some- 

 what higher position than it previously occupied, and to make it the most con- 



Fig. 301.— Autogamy by means of spiral twistings of stamens and style. 



1 Flower of Commelyna coelestis in its first stage. 2 in its second stage, s in its third stage of development. All in 

 longitudinal section and slightly magnified. 



venient place for insects to settle upon (fig. 301 ^). The arrival of insects which 

 have visited younger flowers is at this stage sure to be accompanied by cross-fer- 

 tilization. This state of affairs, however, only lasts a very short time. The style 

 then winds itself into a spiral, and becomes entangled with the coiled stamens, with 

 the inevitable result that the stigma comes into contact with one or other of the 

 anthers, and gets covered with pollen (fig. 301 ^). The whole process occurs in 

 almost exactly the same manner in the flowers of Allionia violacea, of Mirahilis 

 Jalapa, and several other Nyctaginaceas. As regards Allionia violacea, it is only 

 necessary to observe that the flowers are protogynous, that the stigma is higher 

 than the anthers at 6 a.m., when the flower opens, that a few hours later the 

 anthers are raised to a higher level than the stigma in consequence of certain pecu- 

 liar movements of the style and stamens, and that by 10 o'clock the involution of 

 the filaments resulting in autogamy has already begun. In the newly-opened 

 flower of the Marvel of Peru {Mirahilis Jalapa) the dot-like stigma is situated in 

 front of the anthers, and in the event of insects coming in search of honey, it is first 

 the papillae of the stigma and afterwards the anthers that are touched by the 

 intruders. No raising and lowering of filaments or style takes place in this case, 



