128 



ACADEMIC BOTANY. 



LESSON XXV. 



POLLINATION— PEKTILIZATION. 



291. Pollination. 292. Leaf-pollination. 293. Cleistogaray. 294. 

 Parthenogenesis. 295-297. Foreign pollination. 298. Dichogamy. 

 299. Homomorphous, heteromorphous flowers. 300. Modes of foreign 

 pollination. 301, 302. Entomophilous flowers. 303. Sensitive motion. 

 304. Fertilization. 



291. Pollination. — The transportation of pollen, either 

 to the naked ovule in Gymno.spernis or to the stigma in 

 Angiosperms, is called Pollination (L. pollen, poUinis). 

 This has two modes : I. Self-pollination, in which the flower 

 is monoclinous and the stigma receives pollen from the 

 anthers of the same flower ; here the stigmas and anthers, 

 of course, ripen at the same time; II. Foreign pollination, 

 in which the stigma is pollinated by pollen from another 

 flower. 



292. Self- Pollination is called Autogamy (Gr. 

 autos, self; gamos, marriage). It is performed in 

 several ways. In the Mallow (Fig. 182) the stig- 

 mas curl ahout the anthers, receiving the pollen 

 by immediate contact ; though even here the 

 pollen may be brought to them by insects from the 

 anthers of a distant flower, thus securing foreign 

 fertilization. In the 

 Bee Orchis the an- 

 thers open as soon as 

 the flower expands, 

 and the poUinia hang 

 directly over the stig- 

 matic surface, with 

 HI which the lightest 

 breath of air brings 

 them in contact. 

 Furthermore, whilst nearly all other or- 

 chids are incapable of self-pollination, and 

 resort to every form and color to attract 

 insects, the Bee Orchis takes the shape of 

 the bee itself, as if to deceive insects into 

 the belief that a bee is already in posses- 

 sion of the flower and that no other visitor 

 need seek admission. 



293, Cleistogamy (Gr. kleis, key), or locked marriage, is seen in the 



Fta. 1»2.— Gynce- 

 and Androecium 

 Malva rotundifolia. 



Fig. 183. — Autumnal flower of 

 Dead Kettle (Xomium ampUxi- 

 caule). 



