Mr. Hassall on the Structure of the Pollen Granule. 101 



species and in genera of the same family it is pretty uni- 

 form. 



The micrometer employed was a glass one, and divided in 

 the ratio of 249,000 spaces to the inch, 



{5 

 

 249,000 



Lavatera acerifolia {249W 



{91 

 Jl_ 

 249,000 



Fuchsia fulgens J 



Lilium tiffrinum 



Viola tricolor 



Salvia patens 



Length 

 Anagallis arvensis . . J 



Breadth 



Bauera rubioides 



l_^49,000 

 \249,000 



Myosotis palustris , < --^ 



Mimosa marginata < 



249,000 



The colour of the pollen is extremely various and often bril- 

 liant. In Gilia achilletefolia and Petunia violacea it is of a 

 dark blue. In Collomia rosea it is of a bright caerulean blue ; 

 deep red in Cleome spinosa ; of a reddish brown or maho- 

 gany colour in Lilium tigrinum ; and scarlet in Hiichera 

 americana and Verbascum Thapsus. In Papaver Rhosas and 

 Tulipa Gesneriana nearly black. In Convolvulus sejnum opake 

 white ; and yellow, the most common colour of the pollen, in 

 Lilium album and longijiorum, owing to the dense yellow- 

 coloured secretion with which the granules are covered. Dr. 

 Lindlcy says that the pollen occasionally assumes every co- 

 lour except green ; it is however perfectly green in Pentstemon 



