VEGE 7"A TIVE KEPROD I 'CTION. 



251 



the sporangia burst, or arc moist and sticky, adhering to 



each other in larger or smaller 



clusters (fig. 264). Sometimes, 



as in orchids and milkweeds, they 



are all held together in one mass 



by the remnants of the mother 



cells in which they were formed, 



and are attached to a part of the 



tissue of the anther which carries 



the mass as a stalk or handle (figs. 



272, 273). Dry spores are usually FlG 270 _ Ma * re condition of the 



adapted to distribution by wind ; 



while the adherent spores are 



adapted to carriage by small ani- L 



mals, especially insects. (See further ^f 481.) 



352. Germination in place. By the time the sporangia 



about 3 diam ' 



B 



Fir,. 271. Pollen grains. A, white water lily (Xymphtpa alba}. B, a thistle (Cirsimii 

 nemorale). C, a mallow (Hibiscus ternatus}. D, dandelion (Taraxacum offi- 

 cinale}. Magnified 200 diam. After Kerner. /;, pine, showing bladdery enlarge- 

 ments, /, b, of the outer layer of the cell-wall. The central portion is the body of the 

 spore filled with protoplasm with a large nucleus. From it is separated a lenticular 

 cell,/, the rudiment of the gametophyte. Magnified 400 diam. After Strasburger. 



are old enough to release the spores, the latter have already 

 germinated and begun to form a new sexual plant, the male 

 gametophyte. Thus the spores of the non-sexual plant give 



