August. 1921 



GLEANINGS IN BEE CULTURE 



487 



PROTECTION OF NECTAR 



Some of the Adaptations 'which 



Protect Nectar and Pollen from 



Moisture and Theft 



By Prof. K. M. Wiegand 



TH E flower 

 as ail oryaii 

 of the plant 

 has to do with 

 the production 

 of see d, in 

 which process, 

 as is well 

 know n, cross- 

 pollination is es- 

 sential. In fact, many of the most impor- 

 tant features of the flower, such as the 

 showy corolla, scent, and nectar, are provid- 

 ed for the distinct purpose of making more 

 certain this transfer of pollen from the an- 

 ther of the plant where it is produced to the 

 pistil of another plant in the ovary of which 

 young seeds (ovules) are to be "fertilized." 

 Plants, like thrifty human beings, practice 

 a rigid economy in their living conditions. 

 To produce more nectar and pollen than is 

 actually necessary, or to allow these to be 

 injured or stolen, would be inefficient and 

 wasteful. To allow the nectar to be washed 

 away by rain, or carried off by insect visit- 

 ors that would not be effective in securing 

 cross-pollination, would be poor business. 

 We find plants adopting all sorts of means 

 to obviate these dangers, and these contriv- 

 ances are among the most interesting facts 

 connected witli the always interesting sub- 

 ject of floral biology. 



Why Pollen Must Be Protected from 

 Moisture. 

 The pollen of most plants is more or less 

 injured by rain or dew. The pollen grains 

 normally develop tubes in the fluid secreted 

 on the stigma of the flower, and these tubes 

 grow down thru the tissue of the style to the 

 ovules below, but in pure water they swell 

 up and for the most part eventually burst. 

 For this reason the botanist who wishes to 

 germinate the pollen in the laboratory arti- 

 ficially must plant his pollen not in pure 

 water, but in a sugar solution approximat- 

 ing in strength the stigmatic fluid. Conse- 

 quently we find various methods employed 

 by the plant to protect the pollen from the 

 wet. In most cases the same means em- 

 ployed to protect the pollen is equally ef- 

 ficient in protecting the nectar. These meth- 

 ods have been studied by the Austrian bot- 

 tanist Kerner, who has noted a number of 

 ways in which this is accomplished. 

 Protection by Hanging Position. 

 Some plants have bell-shaped, urn-shaped, 

 cup-shaped, or tubular flowers which are 

 pendent on curved stalks. The rain falls on 

 the outside of such a flower without wetting 

 the stamens which are within. A few flowers 

 of this type are the blueberries, bluebells, 

 foxglove, lily of the valley, and basswood, 

 but there are many others. Such flowers 

 are always open for the visits of insects 

 while at the same time they are always pro- 

 tected from sudden showers. A modification 

 of this type is where the whole flower clus- 

 ter is pendent as in the black cherry and 



chokecherry. A 

 more distinct 

 modification of 

 the same method 

 is found in those 

 cases where the 

 flowers assume 

 a pendent posi- 

 tion only in wet 

 weather or at 

 night when the dew is liable to be heavy. 

 This change in position of the flowers is 

 effected either by a curvature of the pedicel 

 of the flower or by a general drop of the 

 whole flower cluster or in some cases by a 

 nodding curvature of the whole top of the 

 plant. Anemones, herb robert, chickweed, 

 potato, English daisy, sow thistle, coltsfoot, 

 buttercups, certain bluebells, and a great 

 many other plants show this movement in 

 rainy weather or at nightfall. 



The iiectar is protected from rain in the basswood 

 by the hanging: position of the flowers. 



Another common and efiicient method of 

 protection lies in the ability of some flowers 

 to close in rainy weather or at night. In the 

 case of simple flowers it is the corolla or per- 

 ianth which closes, as in the crocus, tulip, 

 ])eony, rose, jimson weed, water-lily ane- 

 mone, California poppy, and other species. 

 The California poppy is especially interest- 

 ing because, instead of the whole flower 

 closing, each of the four petals forms a 

 little tent over the pollen and nectar at its 

 base, while the stamens, which have shed 

 their pollen into the base of the flower re- 

 main exiDOsed. In other so-called compound 

 flowers, such as some members of the sun- 

 flower, of which the New England aster, 

 dandelion, salsify, and devil's paint brush 

 maj^ be mentioned, the set of ray flowers 

 close together so that the flower appears to 

 be yet in bud. 



Another rather common method by which 

 the pollen is protected, altho not the nectar, 

 lies in the so-called hygroscopic nature of 

 the anther walls in many plants. On the 

 approach of wet weather the anthers, which 

 have opened to allow the escape of pollen, 

 close up again. This condition can be seen 



