Notes on Pollen. By Lord Avehury. 499 



• 042 mm. in length and • 024-0 • 028 in breadth. It is therefore 

 a short pollen. 



R. scleratus (figs. 25-27), B. Jlammida, H. hetero23hyllns, B. 

 hederaceus, R. repens, R. bulhosus, and R. peltatus are similar. 



In R. acris (figs. 20-22, 30-35) the pollen, at first spherical, 

 assumes various angular, square, and rhomboid forms, sometimes 

 broadly but irregularly elliptic. It is about as broad as it is 

 long, and is covered with minute acute points. It is a very variable 

 pollen (figs. 30-35). In R. auricomus and R. lingua also the pollen 

 is often, if not generally, 4-furrowed. 



In Trautvctteria, palmata, CaWia palustris, Eranthis hyemalis, 

 the pollen is sometimes square, but generally elliptic and broader 

 at one end. The difference of form is perhaps due to the position 

 taken up at first by the pollen while still spherical. 



In Activa spicafa the pollen is small, oval, broadly rounded at 

 the end, colorless, viscid, and almost echinulate with projecting 

 points. 



Trollius agrees with Caltha in many respects, but there is a 

 marked difference in the structure of the stigma. In Caltha it is 

 papillose, in Trollius the surface consists of glassy domed cells. 

 The sepals are incurved and concave, so that insects can only reach 

 the nectaries by using the stigma as a platform. The breast and 

 underside must under these circumstances deposit pollen on the 

 stigma, and papilla? would therefore be unnecessary. 



The pollen of Aconite {A. napellus) is of the usual type, but 

 narrow, the ends being pointed. Aquilegia (figs. 28, 29) forms a link 

 between this form and that of Ranunculus. 



The pollens of Thalictrum flavum, T. aquilegifolium, and T. 

 minus are a 4-6-sided plano-convex disk. 



According to Edgeworth * the pollen of Thalictrum flavum is 

 subspherical with a liroad equatorial band, bearing many pores, 

 and a large crater at each end. T.glaucum,he says, lias two forms 

 of pollen : one elliptic, the other spherical with six bands. This I 

 very much doubt. 



The species of Anemone appear to differ considerably. The 

 pollen of A. nemorosa is of the common ellipsoid form and smooth ; 

 according to Edgew^orth that of ^. alpiina is subspherical and rough ; 

 while that of A. pavoniiia is spherical, and verrucose with rounded 

 knobs. 



A second distinct type consists of a more or less hemispherical 

 disk, with straight edges at the base to the number of 5-7 and 

 facets all over the convex surface, wdth a pore in each. The more 

 highly developed ones have a central facet with one or two con- 

 centric circles of facets round it. Eepresentatives of this type are 

 Clematis Jackman7ii (figs. 36-39), Thalictrum aquilegifoliuin, T. 

 flavum, T. angustifolium, T. minus var. medium, T. majus, T. 



* Pollen, p. 91. 



