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



through apertures placed in a line round the centre of the granule. 

 See fig. 99. 



Juglans regia. 



UlMACEjE. 



Pollen granule spherical, emitting five pollen tubes. 

 Ulmus campestris. 

 Urticace.e. 

 Pollen granule spherical, emitting three pollen tubes. See tig. 100. 

 Parietaria officinalis. Urtica dioica. 



Betulace^. 

 Pollen granule either circular or quadrangular, according as three 

 or four pollen tubes are emitted from it. 



Alnus glutinosa. Betula alba. 



CUPULIFER^ OR CORYLACE^. 



Pollen granule cylindrical, three-lobed. 



Quercus robur. Castanea vesca. Ostrya vulgaris. 



The majority of granules in Ostrya vulgaris are four-lobed. 

 Pollen granule nearly spherical, furnished with three membranes, 

 and emitting three pollen tubes. 



Corylus Avellana. 



ApOCARPOSvE. 



Crassulace^. 

 Pollen granule cylindrical, three-lobed. See fig. 102. 

 Sedum glaucum. Crassula coccinea. 



Saxifragace^, 

 Pollen granule cylindrical, three-lobed. 



Heuchera americana. Adamia cyanea. 



Saxifraga longifolia. Hydrangea nivea. 



S. umbrosa. 



Baueraceje. 

 Pollen granule cylindrical, three-lobed. See fig. 103. 

 Bauera rubioides. 



Leguminos^ or Fabace^e. 



Rectembri^. 

 Tribe Mimose^e. 

 Pollen granules very small, united in fours or multiples of four up 

 to sixteen. See fig. 104, 105, 106, 107. 



Pollen granules united in fours, spherical, three upon the same 

 plane and one resting on these. See fig. 104. 



Mimosa IVIexicana. Mimosa marginata. 



Pollen granules cohering in eights, each emitting two pollen tubes, 

 the third being suppressed by the union of the granules. See fig. 

 105. 



Acacia rigens. 



Pollen granules cohering in twelves. See fig. 106. 



