448 



RELATION TO ENVIRONMENT. 



stamiiio'.lium is so wriipped around the flattened style that the anther lies 

 cloi>Ldy pressei.1 ai^^ainst the face of the style, near the margin opposite that 

 on lohich the stigma lies. 



863, The walls of the antlicr locules ^vhich lie against the style become 

 changed to a sticky substance for their entire length, sw that they cling 



firnih' to the surface of the st^'le 

 and also to the mass of pollen 

 within the locules. The result is 

 that when the flower opens, and 

 this staminodium unwraps itself 

 from the embrace of the style, the 

 mabs of pollen is left there de- 

 posited, while the empty anther is 

 turned around to one side. 



668. Why does the flower de- 

 posit its own pollen on the style? 

 Some have regarded this as tlie act 

 of pollination, and have concluded, 

 therefore, that cannas are neces- 

 sarily self pollinated, and that 

 cross pollination does not take 

 place. But wlu' is there such evi- 

 dent care t(.> deposit the pollen on 

 the side of the style awav from the 

 stignuitic margin ? If \\'e visit the 

 the .staiuen, eannas some morning, when a 



number of the flowers liave just <.)pened, and the bumblebees arc humming 

 around seeking for nectar, we may be aljle t(.> unleick the secret. 



864. We see tiiat in a recently opened canna flower, the petal which 

 directly faces the style in front stands upward quite close to it, so that the 

 flower now is somewhat funneUhajied. This front petal is the labelluui^ and 

 is the landing place fur the bumblebee as he alights on the flower. Here 

 he comes humming along and alighls on the labelluni with his head so close 

 to the style that it touches it. But just the instant that the l>ee attempts to 

 crowil down in tJie flower the labellum suddenlv bends downward, as shown 

 in fig. 468. In so doing the head of llie bumblebee scrapes agahist the 

 pollen, bearing some of it iy{{. Now while the bee is sipping the nectar it is 

 too far below the stigma to dejjo.sit any ]-)olUn on the latter. When the bum- 

 blebee flies to another newly <iiiened flower, as it alights, some of the pollen 

 of the former flower is brushed on tlie stigma. 



865. One can easily ilenion.-trate the sensitiveness of the lalxdium of 

 recently opened tanna llower-, if Hir labellum lias not alread\' moved down 

 in response to some stimulus. Take a lead-pencil, or a knife 'blade, or even 



I ig. 470. 



Canna flriuers \Mth the ]>erianth remo\-cd to 

 sliovv the dc;]ji>biting of the po Icn uii the btyle by 



