Mr. Hassall on the Structure of the Pollen Granule, 559 



AlTRANTIACEiE. 



Pollen granule, in its primary condition, four-lobate ; subsequently 

 it becomes circular, and emits four pollen tubes. See fig. 118. 

 Citrus Aurantium. C. Limonium. 



Lythrace^e. 

 Pollen tube cylindrical, three-lobed. 



Ly thrum Salicaria. Cuphea viscosa. 



Tiliace^e. 



Pollen granule spherical, furnished with three membranes ; extine 

 not covering entirely the exintine. See fig. 119. 



Tilia europaea. Tilia americana. 



Malvaceae. 



Pollen granule globular; extine reticulated, spinous, and per- 

 forated with apertures, fitting into which, in many species, are 

 circular detached pieces of membrane ; apertures very numerous, 

 amounting in some genera to between fifty and sixty ; each reti- 

 culum is the seat of either a spine or an aperture. See fig. 120. 

 Hibiscus liliflorus. Althaea officinalis. 



H. syriacus. Malva sylvestris. 



H. annuus. M. fragrans. 



Pavonia praemorsa. M. virgata. 



Lavatera acerifolia. Kitaibelia vitifolia. 



Pollen granule with but three pollen tubes. See fig. 1*21. 

 Aubutilon striatum. 

 Cistace^e. 

 Pollen granule cylindrical, three-lobed. 



Cistus Helianthemum. 



LlNACEiE. 



Pollen granule somewhat square, emitting six pollen tubes, one 

 from each angle of the figure, and one on either surface. See fig. 

 122. Linum usitatissimum. 



Cylindrical, three-lobed. 



Linum africanum. 



.^EsCULACEuE. 



Pollen granule cylindrical, three-lobed. 



^Esculus hippocastanus. 



AcERACE^E. 



Pollen granule cylindrical, three-lobed. 



Acer Pseudo-platanus. 



PoLYGALACEjE. 



Primary form of pollen granule cylindrical, fluted; extremities 

 truncate, in water becoming spherical and emitting about twenty 

 pollen tubes. PL XVII. fig. 123, 124, 125. 



Muraltia filiformis. Polygala myrtifolia. 



M. Myxta. P. speciosa. 



Polygala grandiflora. P. Chamaebuxus. 



