VEGETA TIVE REPRODUCTION. 



251 



ng to 



the sporangia burst, or are mois 



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 



adapted to distribution by wind; fSSdtf-^lf^o? 



while the adherent spores are t^t^T^^t^. 



adapted to carriage by small ani- L%^ Fra M k agnified ab ° Ul 3 ***' 



mals, especially insects. (See further^]" 481.) 



352. Germination in place. — By the time the sporangia 



270. - Mature condition of the 



Fig. 271.— Pollen grains. A, white water lily (Nymf h ten alba). B, a thistle (Ctrswm 

 >ii-mo>aU-). C.a mallow {Hibiscus ternatus). D, dandelion {Tat 

 cinale). Magnified 200 diam.— After Kerner. E, pine, showing bladdery enlarge- 

 ments, *,*,oi the outer layer of the cell-wall. The central portion is the body of the 



spore filled with protoplasm with a large nucleus. Kroin it is separated a lenticulai 

 cell, /'. the rudiment ot tile gainetuphyte. Magnified 400 diam -Alter Strasburgei 



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 



