552 Mr. II assail on the Structure of the Pollen Granule. 



is a fissure, in connexion with which is a small strip of membrane. 

 PL XV. fig. 62, 63. 



Plumbago rosea. P. caerulea. 



PlaNTAGINACEjE. 



Pollen granule small, circular, perforated with about ten apertures 

 for the escape of pollen tubes. It is probable that the number of 

 apertures in each granule is determinate, but it is no easy matter to 

 ascertain what that is exactly. See fig. 64. 



Plantago lancifolia. P. oblongifolia. 



Dipsace^e. 



Pollen granule three-lobed in its dry state, extremities not taper- 

 ing and nearly truncate ; in connexion with each of the fissures is 

 almost invariably a piece of membrane of not any very defined form : 

 extine spinous, with traces of reticulation ; in water becoming nearly 

 triangular and emitting three pollen tubes. 



Scabiosa caucasica. Dipsacus fullonum. 



S. atropurpurea. D. sylvestris. 



Composite. 



Pollen granule of the following species of Cynaracea does not 

 differ materially from that of the preceding order Dipsacece ; the 

 spines are however more strongly marked. See fig. 65, 66. 



Centaurea scabiosa. Arctium Lappa. 



Cnicus Marianus. Echinops sphserocephalus. 



C. nutans. Cynara scolymus. 



C. tenuiflorus. 



Pollen granule polyhedral, emitting three pollen tubes ; extine co- 

 vered with a raised hexagonal reticulation of some breadth, on which 

 are. placed a number of spines touching each other. See fig. 67. 

 Scorzonera hispanica. 

 Pollen grain small, if examined in a sufficiently early stage of its 

 formation trilobate ; subsequently becoming spherical or triangular 

 and emitting three pollen tubes ; extine covered with strong spines. 

 No pieces of membrane in connexion with the fissures. See fig. 68, 69 . 



Leontodon Taraxacum. Pascalia glauca. 



Siegesbeckia orientalis. Silphium cornutum. 



Catananche cserulea. Helianthus annuus. 



Relhania pungens. Dahlia glabrata. 



Senecio nemorensis. Inula Helenium. 



Ozothamnus cinereus. Solidago Virgaurea. 



Tanacetum vulgare. Tussilago Farfara. 



Artemisia vulgaris. Eupatorium purpureum. 



Chrysanthemum viscosum. Chrysocoma coma-aurea. 



Anthemis nobilis. Cineraria Andersonii. 



Bellis perennis. 



Eptgynos^e. 



Stellate or Galiace^e. 

 Pollen granule oval, extine containing about eight longitudinal 

 fissures. See fig. 70, 71. 



Crucianella stylosa. Galium porrigens. 



