CH. XIIl] GERMINATING POLLEN. 175 



of pollen may be watched by cultivating the grains in 

 sugar solution, or the pollen may be made to germinate in 

 a natural manner on the stigma, which must then be 

 examined in longitudinal sections. A section of this sort 

 is diagrammatically represented in fig. 81. The pollen- 



Fm. 81. 



DIAGKAMMATIC SKETCH or POLLEN GRAINS, germinating on the stigma 

 of (Enothera, the Evening Primrose. The tissue in the interior of 

 the section is not shown. 



grains of the Evening Primrose are triangular in outline, 

 and the angles are the places whence, in the process of 

 germination, the hypha-like pollen-tubes grow forth. It 

 passes between the superficial cells of the stigma and 

 burrows like a fungus in the tissues of the style. It feeds, 

 as it grows, on the tissues through which it passes, so that 

 it not merely resembles a fungus hypha in appearance, 

 but also behaves like one, being in fact, for the time being, 



