146 THE VEGETABLE WORLD. 
each lobe in the Barberry, and two for each lobe in the Persian 
Laurel, as represented in the engravings. 
A familiar acquaintance with the microscopic structure of the 
Fig. 193. Fig. 194. Fig. 195. 
Stamens of Solanum, Barberry, and Persian Laurel. 
pollen of vegetables gives rise to some very curious speculations. 
en a microscope of considerable power is employed, we find 
that the forms of these grains vary very considerably in different 
species, some of their forms being of a very elegant description. 
The pollen-grain is generally composed of a sort of double 
covering, the innermost containing a mucilaginous liquid, named 
Horilla. Figs. 196 and 197 are the pollen-grains of the Hollyhock; 
having a sort of double sac or covering surrounding each graim- 
The external membrane of the globule of pollen is smooth, dotted, 
granulated. It is covered with small prickles, or finely reticulated, 
according to the species. It also exhibits folds and pores. In the 
pollen of Wheat (Fig. 198) there is only one pore; in the Primrose- 
tree (Fig. 199) there are three. Figs. 200, 201, and 202 show 
the pollen grains of Garlick, the Phlox, and the Melon. The 
number of pores in a pollen-grain may reach five or even eight. 
These pores perform important functions, as we shall soon see. 
When a grain of pollen is placed in water it swells, because it 
absorbs a certain quantity. of the liquid. Its membranes expand, 
and the internal one protrudes through the pores of the external 
membrane. The vessel bursts, and the florilla escapes in a sort © 
mucous and granulous jet. This is an anomalous but very curious 
phenomenon to observe. It is anomalous, because it is not thus 
