AUTOGAMY IN HETEROSTYLED FLOWERS. 397" 



and inflection, which result in bringing the stigma underneath the anthers, so that 

 when the latter shrivel their pollen must fall upon the receptive tissue. Of the 

 host of observations relating to this matter, we can here only select a few to serve 

 as examples, and the most suitable for our purpose will be the Primulas, to which 

 reference has already been frequently made, viz. Primiula Auricula, P. glutinosa, 

 P. longißora, and P. minima. 



The corolla in the short-styled flowers of Prirnula Auricula has a comparatively 

 large expanded limb, the surface of which is slightly concave; the five stamens are 

 adnate to the contracted throat of the corolla, where the tube passes into the 

 limb, and the anthers form, at that part of the flower, a ring through the middle of 

 which insects must penetrate in order to enter the floral interior. The style is short, 

 and the spherical stigma at the top of it stands at a level corresponding to only a 

 third of the length of the corolla-tube. At the time when the dehiscence of the 

 anthers takes place, the flowers are in a nodding or horizontal position. In these 

 circumstances no pollen can reach the stigma, and, unless visited by insects, the 

 flower remains unpollinated until it fades, nor does the fall of the corolla operate as 

 a means of conveying pollen from its own anthers to the receptive tissue. It is quite 

 diflferent with the long-styled flowers of the species in question. The limb of the 

 corolla is rather smaller, and is hollowed into the shape of a basin; the five stamens 

 are adnate to the lowest third of the tube, and their anthers stand at the same height 

 as does the stigma in a short-styled flower. The style is long, and the stigma may 

 be seen in the middle of the flower's throat. In other respects there is no diflference 

 worth mentioning between the two forms. The stigmas of the long-styled flowers 

 are liable to be dusted with pollen brought by insects from the anthers stationed in 

 the throats of short-styled flowers. Whether this occurs or not, the receptive tissue 

 under any circumstances gets covered with pollen when the corolla becomes detached 

 and falls off", for the stigma is then dragged through the ring of anthers in the 

 corolla-tube, and is certain to remove some of the pollen which still adheres in more 

 or less abundance to them. 



Altogether diflerent is the process of autogamy as manifested in Primula longi- 

 ßora. In this case the corolla of a long-styled flower has a shorter tube and larger 

 limb than that of a short-styled flower. The anthers are situated in the throat just 

 behind the mouth of the corolla-tube. The style is long and projects far beyond the 

 throat, whilst the stigma is held considerably above, that is to say, in front of the 

 ring of anthers. The flowers are either horizontal or else ascend obliquely, and 

 neither of these positions admits of pollen being deposited by the anthers upon the 

 stigma. As in this species the corolla does not drop but persists even when withered, 

 no autogamy takes place in the long-styled flowers when the plant is growing wild. 

 On the other hand, every insect which enters the flower must necessarily touch the 

 stigma, stationed where it is in front of the passage, and cross-fertilization then 

 ensues. The short-styled flowers have a longer tube and smaller limb to the corolla. 

 Their anthers, unlike those of many other Primulas, are situated in the throat close 

 beneath the corolla-limb in the same position as in the long-styled flowers; but the- 



