28 A HALF-HOUR WITH THE 



which is contained a quantity of powder, or dust, 

 called " pollen." The walls of these valves are worth 

 careful examination under the Microscope, on ac- 

 count of the beautifully-marked cellular tissue of 

 which their inner walls consist. The cells of this 

 tissue contain in their interior spiral fibres similar 

 to those which have been described as present in 

 certain forms of vascular tissue. In the anthers of 

 the common furze the fibres are well marked (Fig. 

 116, PI. 5) ; in the common hyacinth they are 

 larger, and frequently present, in their intercellular 

 spaces, bundles of raphides (Fig. 117, PI. 57). In 

 the white dead-nettle the fibre is irregularly de- 

 posited (Fig. 118, PL 5). In 'the anthers of the 

 narcissus (Fig. 119, PL 5) the cells are almost vas- 

 cular in their structure, and present the same 

 appearance as those described under the head of 

 annular ducts. (Compare Fig. 119, PL 5, with Fig. 

 44, PL 2.) In the crown imperial the fibres of the 

 cells radiate from a central point in a stellate man- 

 ner (Fig. 120, PL 5). 



When the anther-cases have been examined, a 

 little of the dust may be shaken on to a slide, and 

 examined as an opaque or a transparent object. 

 Each species of plant produces its own peculiar 

 form of pollen. These little grains are truly cells. 

 They are the cells of plants which, in their position 

 in the anther will not grow any further. They are 

 destined to be carried into the pistil, where, meet- 

 ing with other cells, they furnish a stimulus to their 

 growth, and the embryo, or young plant, is pro- 

 duced. The history of the development of these 

 cells, as well as of those in the interior of the pistil, 

 is a very interesting one, and is one of those sub- 

 jects of investigation which has been created by 

 the aid of the Microscope. The pollen grains vary 

 in size as well as form. They are frequently oval 



