170 



ELEMENTS OF BOTANY. 



earlier stage (above), but it cannot deposit any pollen on the 

 stigmas which are unripe, shut together and tucked aside, out 

 of reach. On flying to a flower in the later stage the pollen 



II 



III 



IV 



Fia. 153. — Provisions for OrossrFertilization in the High Mallow. 



I, essential organs as found in the bud ; II, same in the staminate stage, the anthers 

 discharging pollen, pistils immature ; III, intermediate stage, siig, the united 

 stigmas ; IV, pistillate stage, the stigmas separated, stamens withered. 



just acquired will be lodged on the prominent stigmas and 

 thus produce the desired cross-fertilization. 

 Closely related flowers often differ in their 

 plan of fertilization. The high mallow, a 

 plant cultivated for its purplish flowers, which 

 has run wild to some extent, is admirably 

 adapted to secure cross-fertilization with its 

 own pollen, since when its stamens are shed- 

 ding pollen, as in Fig. 153, II, the pistils are 

 incapable of receiving it, while when the pis- 



Fjg. 154.— stamens '■ ° ' ^ 



and Pistils of tils are mature, as at IV, the stamens are 

 Eound-Leafed quite withered. In the common low mallow 



Mallow (the stig- 

 mas curled round ot our door-yards and waysides, insect f erti- 



among the sta- Hzation may occur, but if it does not the 



mens to admit of 



self-fertilization), curling stigmas finally come in contact with 



