Sates on Pollen. Bij Lord Avebury. 507 



with three rather shallow furrows, three pores, and finely netted on 

 the surface {Armeria, Statice). The pollen is large. 



According to Edgeworth the pollen of /S'^rti! ice ^a//or(^n is spherical 

 with a punctured surface. 



PRLMULA.CE.E. — The commoner type is the usual ellipsoid form 

 with three furrows. 



In Primula ohconica the pollen is triangular, sometimes quad- 

 rangular, with the pores on the angles and a tripodial or tetra- 

 podial furrow on the centre, the three or four arms running to 

 the angles. 



Our Primrose and Cowslip have a barrel-shaped pollen with 

 truncate ends, and six, seven, or eight furrows. Other species have 

 as many as twelve. The pollen of the short-styled flower is -g^^ in. 

 in length, that of the long-styled only y^qo ^^- ^ ^^^^^ ^°^' how- 

 ever, enter into the interesting problems presented by these pollens, 

 wliich have been so well described by Darwin and others. 



Oleace^e. — The species of this order which I have been able 

 to examine have pollen of the common ellipsoid type with three 

 furrows. 



Apocynace^. — The pollen of Vinca is large, oblong, rather 

 truncate at the ends, 3-furrowed, with the furrows on the angles, 

 and very viscid. 



The side view of the pollen of Nermm oleander is oblong and 

 truncate at the ends ; while the end view is square with a pore in 

 the centre. 



Gentianace^. — The predominant form is oblong-ellipsoid with 

 the usual three furrows and rounded ends. 



Villarsia ovata has a triangular pollen with a tiipodial ridge 

 and a triangular depression in the centre. 



CoNVOLVULACE^. — There are three or perhaps four distinct types 

 of pollen in this order with many minor modifications. That of 

 Convolvulus arvensis, our small Convolvulus, is of the common 

 ellipsoid type with three fvirrows. Similar pollens occur in C. 

 cneoncm, C. tricolor, C. scammonia, and in Cuscuta. 



Our large Convolvulus, C. (Cali/stegium) sepium, has the pollen- 

 grains hemispherical, with three concentric circles of not very well 

 marked facets. Tlie pores are numerous (16-20) and scattered 

 over the whole surface. The lower side is deeply concave. 



Ipomcea digitata has a spherical pollen, covered with long, stout, 

 and frequently curved spines, each set in a circular or hexagonal 

 depression. 



BoRAGiNACEiE (figs. 56-58). — The dumb-bell shape of pollen, 

 though not universal, is very general in, and characteristic of, this 

 great order. The constriction is specially marked in Myosotis, Litho- 

 spermum,, and Aspcrugo among English species. 



The size naturally differs, but as a rule is small. The dumb- 

 bell form is perhaps due to the fact that the longitudinal furrows 



2 M 2 



