506 Transactions of the Society. 



spiny, spherical (fig. 15), or oblong (fig. 55), and in end view round or 

 somewhat triangular. In the larger and more spherical forms the 

 fuiTows are shallow, and more or less hidden by the spines. 

 Owing to the shortness and width of the pollen there is in many 

 species little difference between the side and end views. 



In some species {Chicoriace^, Leontodon, Tragopogon, Hieracium, 

 Greins, etc.), the pollen is more or less distinctly faceted. 



Of special interest are the Centaurcas and Artemisias. The pollen 

 of Centaur ea is oblong, and while C. nigra (figs. 53, 54) and G. Jacea 

 have stout, if short, spines, C. scahiosa and prealta have longer, finely 

 echinulate pollen, while in C. cyanus, C. montana and C. dealhata 

 it is perfectly smooth. The furrows are much more conspicuous 

 than in the order generally. The smooth pollens make up for the 

 absence of spines by increased stickiness. I have not been able to 

 satisfy myself why Centaurea should differ so much from the rest 

 of the order. 



The Artemisias present us with transitions from entomophilous 

 to anemophilous pollen. 



According to Edgeworth Centaurea calcitrapa has three forms : 

 (1) globular, echinulate ; (2) oval, echinulate ; (3) oval, smooth. 



Artemisia lactijlora has conspicuous heads of white flowers, as 

 tlie name denotes, it is slightly fragrant, and the pollen is spiny or 

 echinulate. These characters point to insect agency ; but, on the 

 other hand, the pollen soon dries, and is easily floated away by the 

 wind. 



Kirchener describes some alpine species {A. glacialis and A. 

 mutellina) also as entomophilous. 



In A. vulgaris the pollen is* smooth, dry, and easily carried 

 about by the wind. The form is elliptic. Other species have 

 almost spherical pollen. 



Campanulace^. — Several types of pollen occur in this order. 

 Lobelia and some others have the common ellipsoid form, with 

 three furrows and three pores. The Campanulas, or at least those 

 I have examined, have spherical echinulate pollen ; that of Jasione 

 is also spherical, but granular. Campanula sarmatica, according 

 to White's drawings, has a smooth globular pollen; and in C 

 hederacca, according to Edgeworth, it is smooth and dodecahedric. 



VacciniaceyE. — The pollen is in tetrads, the four grains being 

 more or less completely compacted. They are often triangular, 

 with obtuse angles, but those of Vaccinium myrtillus are globular. 



Ericace^. — The Ericacefe also have their pollen as a rule in 

 tetrads, generally arranged in pairs at right angles to one another. 

 In some species of Khododendron the tetrads are joined by threads. 

 The free ends of the grains are sometimes obtuse, sometimes 

 pointed. 



Clethra and Enkianthus have free pollen grains. 



Plumbaginace^. — The common type is oval or roundly oval. 



