Mr. Hassall on the Structure of the Pollen Granule. 563 



Magnoliace^. 

 Pollen granule elliptical, tapering towards either extremity, with a 

 s'myle furrow running down its long axis. PI. XVIII. fig. 150. 

 Magnolia grandiflora. Magnolia glauca. 



Nymph^ace^. 

 Pollen granule oval, with but a single furrow passing down one 

 side. See fig. 151, 152. 



Nymphsea alba. Nymphsea lutea. 



FUMARIE^. 



Pollen granule furnished with three membranes, spheroidal ; extine 

 perforated with six apertures for the passage of pollen tubes ; four of 

 these are placed on a line dividing the granule into two hemispheres, 

 in the centre of each of which one of the two remaining apertures is 

 situated. See fig. 153. 



Fumaria officinalis. F. lutea. Diclytra formosa. 



Obs. — Most of these granules in the last two sjiecies appear to be 

 imperfectly formed, having but three or four pollen tubes ; but the 

 presence of three membranes in them all, and the occasional appear- 

 ance of a perfectly formed granule, prove that there is no essential 

 diflference in the pollen of the three species. 



Papaverace^. 

 Pollen granule cylindrical, three-lobed. 



Papaver Rha?as. Argemone mexicana. 



P. somniferum. Glaucium luteum. 



Pollen granule spherical, with six fissures for the escape of pollen 

 tubes. See fig. 154, 155. 



Eschscholtzia californica. 



Ranunculace^. 

 Pollen granule cylindrical, three-lobed. 



Pseonia corallina. Helleborus foetidus. 



Aconitum Napellum. H. niger. 



Delphinium Staphysagria. Thalictnim minus. 



Aquilegia vulgaris. Clematis Flammula. 



Pollen granule mostly four-lobed, cylindrical, in water becoming 

 square and emitting four pollen tubes. See fig. 156, 157, 158. 

 Ranunculus acris. 

 Obs, — The term cylindrical, as applied to that form of pollen 

 granule distinguished by the presence of three furrows, which divide 

 it into three more or less prominent lobes, is perhaps objectionable, 

 inasmuch as it is not properly cylindrical, and should have been re- 

 moved for a more appropriate one, were it not that it has already 

 been employed in that portion of the paper already published. All 

 that is intended to be conveyed by the term is, that all pollen to which 

 it is applied is of an elongated form. 



One of the first things to be remarked, on a revievv^ of the 

 ))receding descriptions, is the great and striking simphcity of 

 ibrm and structure which characterizes the pollen of endo- 

 genous plants, compared with exogenous ; and not alone is 



