480 ^ Transactions of the Society. 



is not conclusive, because the reduction may be close tc the pores, 

 and possibly not carried all along the furrows. 



Colours. 



Pollen is often brilliantly coloured ; as a rule it is a golden 

 yellow, but orange in Da'pline odora, Crocus, BtUomus, Lamium 

 purpureum, Lilium auratum ; green or greenish-blue pollen from 

 the long stamens of the mid-styled and short-styled flowers of 

 Lytlirum, while the pollen of the short stamens is yellow. 



Violet. — Pcdicularis sylvatica ; Populus tremula ; Geranium 

 pratense. 



Indigo. — Papaver Rhmas. 



Purple. — Anemone coronaria ; Xanthorhiza apiifolia. Those 

 of some Willows are purplish. 



Topaz. — Zea mays. 



White. — Viola striata ; Polemonium reptans. 



Colourless. — Corydalis loilsoni, with purplish reflexions. 



Generally, indeed almost universally, the pollen of one species 

 is of one colour, but, as already mentioned, that of Lythrum is an 

 exception. 



The Form and Texture of Pollen. 



The pollen of different species present great differences in form 

 and texture, thus offering innumerable problems of much interest. 

 For some, I tliink, probable explanations may be suggested, but 

 many still await solution. 



By far the commonest form is more or less elliptic, with a 

 smooth surface, as was long ago pointed out by Fritsche, in his 

 admirable memoir, Bei. zur Kenntniss des Pollen.* Kernerf esti- 

 mates this form as occurring in quite half of all flowering plants. 



Much pollen is spherical, smooth in some species, spiny in 

 others ; some is hemispherical, some faceted, some dumbbell- 

 shaped, some triangular, some barrel-shaped, some filamentous ; 

 and there are a variety of other shapes. 



Again, some pollen is dry, some is sticky. When pollen is 

 intended to be carried by the wind, it is obviously an advantage 

 that it should be dry, smooth, and spherical. 



Entomophilous Spieeies. 



Very different are the conditions in entomophilous species. 



1. There is a great economy of pollen. While a nettle will 

 produce millions of pollen-grains, and a Scotch fir will colour the 

 ground yellow, in entomophilous species the quantity is much less. 



* Berlin, 1832, t Nat. Hist, of Plants, vii. p. 98. 



