POLLINATION OF THE BLUEBERRY ELOWER. 



77 



Fig. 27. — Flowers of the blueberry, from 1908 seed- 

 lings of tbe large-berried New Hampshire hush of 

 Vdcciniuni cortpnhosiim : a. Flower of the cori/m- 

 bosum type of plant ; h, flower of tbe amocniini type 

 of plant : c, same as b, but part of tbe corolla re- 

 moved to show the stamens, style, and stigma. 

 (Enlarged .''. diameters.) 



The operation of the mechanism for releasing the pollen may be 

 observed with a high-power hand lens. The stamens hang in a close 

 circle about the style. The filaments are broad and laced into a tight 

 tube by the interweaving of their marginal hairs, the anther sacs 

 press close together, and 

 therefore the only con- 

 venient way of access to 

 the nectar is through the 

 slits between the anther 

 tubes. The anther tubes 

 are stiff and when one of 

 them is pushed to one 

 side the movement is 

 communicated to the an- 

 ther sac. The pollen if 

 mature is dislodged and 

 falls down the tube and 

 out at the orifice. 



The pollen does not 

 come out of the anthers 

 readily on a cloudy, humid da}^, but on a warm, sunny, dry day it 

 accumulates in the tubes and when they are moved it runs out like 

 grain from a grain chute. The pollen grains (fig. 29) do not stick 

 to the sides of the parchment-like anther tubes when these are dry, 

 but they have the faculty of adhering to hard surfaces, such as glass 



or the lead of a lead pencil, and 

 they doubtless would adhere also to 

 the hard shell of an insect whether 

 it was covered with hairs or not. 



The pores of the anther tubes do 

 not open squarely across the ends 

 of the tubes, but they are set on a 

 long bevel facing inward. The 

 j)ollen when released would there- 

 fore fall upon the stigma Avere it 

 not for a peculiarity in the struc- 

 ture of that organ. The sticky 

 stigmatic surface, which the pollen 

 must reach to eftect pollination, 

 is at the apex of the globular or top-shaped stigma, while the sides 

 of the stigma as far up as the middle have a dry surface ending in a 

 short collar a little wider, during the earlv maturitv of the stisnia, 

 than the widest part of the stigmatic surface. (See fig. 30.) In the 

 inverted position of the flower the falling pollen strikes this dry 



193 



Fig. 28. — Stamens of the blueberry, from 

 the flower shown in fig. 27, c : a, View 

 from the inner face : b, side view. 

 Both views show the broad filament 

 with hairy margins and the anther 

 sacs, tubes, and pores. (Enlarged .'■ 

 diameters. ) 



