52 Fertilization of Plants. [July, 



second whorl from the centre, in flowers where four regular 

 whorls are developed, we shall observe the breaking up of the 

 cellular tissue of the interior and forming cavities on each side of 

 a middle line which continues unaffected. These cavities are 

 filled with a fluid, or semi-fluid substance, which is to undergo 

 reorganization and become developed into the peculiar organs 

 that constitute an anther and its contents. A later examination 

 will show us that a layer of small compact cells have been form- 

 ed as a lining to the cavities, and that the cavities themselves 

 are filled with large cells, much larger than the original cells 

 which were broken up. These large cells are the generating 

 cells of the pollen. At first they are filled with a semi-fluid sub- 

 stance which soon becomes turbid with minute grains, which as- 

 sociate in groups, forming granular nuclei. These nuclei increase 

 in size and take on a membranous covering, and become pollen 

 grains. As these enlarge the mother cells disappear, yielding 

 their own bodies for the nourishment of their offspring. The 

 perfection of the pollen grains requires not only the consumption 

 of the mother cells, but much of the material that enters into the 

 anther itself, bringing into operation one of those beautiful exhi- 

 bitions of skill and design, which are so profusely scattered 

 through every department of nature's works. The lobes of the 

 anthers are covered by an epidermis like other parts of the plant, 

 but beneath this epidermis is one or more layers oi Jihro cellular 

 tissue, which extends over the interior of the lobes, with the ex- 

 ception of a line, usually running from the base to the summit of 

 the anther, which is not covered by this tissue. The cells that 

 compose this tissue are made up of an elastic fibre, enclosed and 

 confined by a membrane. This membrane is absorbed to perfect 

 the pollen grains, and it is the last portion of the anther absorbed, 

 so that when the elastic fibres are freed from this confinement, 

 the grains of pollen are perfect, and ready to enter upon the 

 functions for which they were produced. As soon as the fibres 

 are free, they exert their elasticity upon the walls of the anther, 

 and by their combined action split the anther along the line of 

 the cells, and expose the pollen to the action of external agents. 



