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. 



Cobaea stipularis 



Lavatera acerifolia 



Geranium sylvaticum 

 Fuchsia fulgens . . . . 



Lilium tigrinum 



Viola tricolor 



Length 



Breadth 



Length 



Breadth 



Salvia patens 



Anagallis arvensis 



Length 



Breadth 



Bauera rubioides 



Myosotis palustris 

 Mimosa marginata 



_249,000 



249,000 



: H 



249,000 



2 

 249,000 



A 3. 

 249,000 



f 

 249,000 



H 

 249,000 



3 



_i 



249,000 



249,000 



j 



249,000 



_i 



249,000 



Tff 

 249,000 



249,000 



249,000 



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

 liant. In Gilia achillecefolia 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 Huchera 

 americana and Verbascum Thapsus. In Papaver Rhceas and 

 Tulipa Gesneriana nearly black. In Convolvulus sepium opake 

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

 Lilium album and longiflorum, owing to the dense yellow- 

 coloured secretion with which the granules are covered. Dr. 

 Lindley says that the pollen occasionally assumes every co- 

 lour except green ; it is however perfectly green in Pentstemon 



