Notes oil Pollen, By Lord Avebury. 475 



The process in Gymnosperms and Cycadae is even more com- 

 plex.* In Geratozamia, for instance, the intine divides and shuts 

 off a small portion of the contents, so that the interior of the pollen 

 is divided into a large and a small cell. Subsequently two or 

 more other small cells are added, so that there is a so-called pro- 

 thallium, comprising three to eight cells. Fig. 1, after Juranyi, 

 shows a pollen-grain of Geratozamia with 3-celled prothallium and 

 nucleus. 



The more the process of fertilization is studied, the more com- 

 plex it is found to be. 



The antherozoids of Seaweeds even have a red "eye "-spot, 

 which, according to Thuret, agrees in chemical composition with 

 the eye-spot of Euglena. 



Pollen retains its life and power for a long time, in some cases 

 for years. 



In many, but by no means in all species it is ready to fertilize 

 the seed almost immediately. In others, even after leaving the 

 parent plant, it requires months to reach maturity. In Pinns, for 



• Juranyi : U. d. Pollen des Gynospermen, Pringsheim's Jahrb., 1872 ; Stras- 

 burger : U. d. Phanerogamen, Jena, 1884. 



EXPLANATION OF PLATES VII. and yui.— continued. 



Fig. 32. — Ditto. Side view of an irregular form, showing two furrows, and fairly 



common. 

 ,, 33.— Ditto. Side view of square form, fairly numerous. 

 ,, 34. — Ditto. End view, showing three furrows. 

 ,, 35. — Ditto. End view, showing four furrows, and fairly common. 

 „ 36. — Clematis Jackmanni. x 100. Four-sided pollen. 

 „ 37. — Ditto. Five-sided pollen. 

 ,, 38. — Ditto. A large, rather flattened pollen. 

 ,, 39. — Ditto. Pollen-grain lying on its side, showing two lateral pores and 



one on the top ; F, flattened base. 

 ,, 40. — Bocconia microcarpa Maxim. x 400. Pollen newly liberated from 



the anther. 

 ,, 41. — Ditto. Pollen when it has subsided into a hemispherical disk, with 



facets. 

 „ 42. — Ditto. Uuder-surface, flattened, and showing the large central de- 

 pression. 

 ,, 43. — Polygala calcarea P. Schultze. x 400. Pollen showing the long axis, 



with four furrows and four ridges, with a small portion of a fifth on 



the right. 

 „ 44. — Ditto. End view of pollen, showing nine ridges and nine furrows. 

 ,, 45. —Stellaria Holostca Linn, x 400. Pollen-grain showing ridges and mark- 

 ings on the surface 

 „ 46. — Ditto. The same grain focused to show the line of points round the 



base. 

 ,, 47. — Poterium sangidsorba Linn, x 400. Spherical pollen, as first liberated 



from the anther. 

 ,, 48.— Ditto. The discoid form ultimately assumed, with 4-6 facets on the 



perpendicular sides of as many faces. 

 ,, 49. — Cluerophyll'uvi temidum Linn. Pollen x 400: Po, Po, pores of the 



extine through which the pollen-tube emerges. 

 ,, 50. — Ditto. Pollen x 800 : Po, Po, pores of the extine situated in the 



furrows. [Fig. 51. 



2 K 2 



