140 Transactions. 



pollen before the others (opposite the petals). Honey is secreted 

 by a little cup-like ring at the base of these outer sepaline 

 stamens, but a rudimentary ring exists also at the base of the 

 others. The styles vary in number, from three to five, and project 

 outwards between these outer erect sepaline stamens. Hence 

 insects visiting the ilower aliglit on the petals and crawl round 

 under the outer stamens so that their sides are touched by the 

 anthers or stigmata. The visitors are in this form (as in almost 

 all) flies of medium size, and probably belonging to a large 

 variety of genera. 



S. Holostea is very similar, but tlie stamens are more curved 

 outwards, so that self-fertilisation by contact of the stigmata and 

 anthers in the same flower is very rare ; the chickweed S. media 

 is on a lower scale, as here the stamens are often reduced in 

 number from ten to sometimes only three, and self-fertilisation by 

 contact happens very frequently. S. graminea has advanced, 

 however, a little, as in this form the styles are lengthened, and 

 the filaments of the stamens are shortened so that contact of the 

 anther and stigma is impossible ; and the eifect of this is shown by 

 the fact that a higher class of flies, such as Syritta pipiens, with 

 more rapid flight and a higher type of mouth, are found on it. 

 S. nemorum is very near S. graminea. 



Cerastium vulgutum and alpinum are a little higher in the 

 scale than S. uliginosa, as in these forms self-fertilisation is pre- 

 vented almost entirely by a difierent artifice ; here the stigmata are 

 not fully ripe till the stamens have dehisced. C. (irvense is 

 distinctly more advanced, for each sepaline stamen is broadened 

 at the base or insertion, and forms with its sepal a sort of 

 miniature canal ; honey is held in this canal, and to a certain 

 extent protected both from evaporation and small short-lipped 

 and thievish flies ; probably it is visited by a higher order of 

 flies or possibly small bees, but I was too late in the season last 

 year to prove this. 



In the genus Arenaria, one finds in A. trinervis the petals 

 much reduced in size, and this enables the flower to secrete a 

 larger amount of honey ; hence, mainly intelligent kinds of 

 Diptera frequent it in spite of its inconspicuous character. A. 

 serpyllifolia, which is a dwarf plant adapted to poor soil, is not 

 quite so rich in honey, and contact of anthers and stigma 

 occasionally happens. ^. jue^j^oufe is utterly difi"erent ; here the 



