504 Transactions of the Society. 



and as they dry assuming a faceted form (fig, 48). On the other 

 hand, those of P. officinale is said to be oval with six furrows. 



Moreover the pollen of P. sanguisorha is dry, while that of most 

 Kosacese is viscid. 



SAXiFKAGACEiE. — The poUen of Saxifraga and of allied genera 

 is of the common ellipsoid form. On the other hand that of the 

 Currants and Gooseberries is of quite a different type, being at first 

 globular, subsiding into a 4-6 sided disk, with a pore in each facet. 



Ckassulace^. — The relationship between this order and the 

 Saxifraga is so close that it is not surprising to find that the pollen 

 belongs to the same type as that of Saxifraga. It varies princi- 

 pally in the breadth or narrowness of the grain and the form of the 

 ends. In some species, Sedum racemosum for instance, the furrows 

 are on the angles. 



Droserace^. — The pollen oi D.rotundifolia is oval and in tetrads. 



HALORAGACEiE. — The pollen of Hippuris is oblong or oval, 

 rounded at the ends, finely granular, and dry. The end view is 

 roughly orbicular with five ridges. 



That of Myriophylhiin is ellipsoid and dry. 



Callitricage^. — Callitricha grows under water, but when 

 about to flower it rises to the surface, the stamens project, and the 

 pollen is emitted into the air. 



Lythrarie^, — The pollen of Lythruni is barrel-shaped with 

 six furrows. The colouring is remarkable, that of the short 

 stamens being yellow as usual, while that of the long ones is blue, 

 or, as seen by some persons, green. It has, however, been so well 

 described by Darwin that I will not allude to it further. 



That of Peplis is barrel-shaped, with six ridges in three pairs 

 on the ansles. 



Onagraoe^e. — The pollen of this order is triangular and in the 

 form of tetrads, or free, and is laced together by numerous fine 

 threads. The individual grains come in contact at one point in 

 pairs placed at right angles to one another. There are three pores 

 situated on the angles. 



CucuRHiTACE^. — The Cucurbitacea3 present three very different 

 types of pollen. That of Bryonia is of the common ellipsoid form 

 with three furrows. 



On the other hand in Cucurhita it is very large, spherical and 

 spiny, with 6-12 pores. That of the Melon {Cucumis) is triangular, 

 with a small knob at each angle, and finely netted. 



Umbellifer^. — The most characteristic pollen of the Umbel- 

 lifers is linear-oblong, rounded at the ends, with three fmrows, which, 

 however, are shorter than the grain, so that they are not visible in 

 an end view. 



The dumb-bell form occurs in many species, as for instance in 

 Chxrophyllum (figs. 49, 50), Conopodium, Pimpinella, Caucalis, 

 Angelica, Heracleum, Carum,, Cicuta, Scandix, Daucus, etc. 



