THE MONTHLY BULLETIN. 



CALIFORNIA STATE COMMISSION OF HORTICULTURE, 

 Vol. III. August, 1914. No. 8. 



POLLINATION OF PLANTS. 



By Dr. A. J. Cook, State Commissioner of Horticulture, Sacramento, Cal. 

 Address before the Fruit Growers' Convention, Davis, California, June, 1914. 



You will each and all recall the mechanism of a flower in its best 

 development. As you know each part of the floral envelope is a 

 modified leaf. The close student often sees positive proof of this in a 

 petal that is also at the same time a stamen. A double flower results 

 from a reversion of stamens in a multi-staminate flower, like the rose, 

 back to petals. 



The outer circle of floral leaves — the sepals — are still leaflike as they 

 usually retain the jjreen color of the normal leaves. These sepals, 

 except as they unfold and protect the bud, function solely as leaves. 

 The next whirl of the floral envelope just within the calyx forms the 

 corolla whicli is made up of three of more variously colored leav&s known 

 as petals. These are what give beauty to the flower and are of real 

 service to it in attracting insects to the important work of pollinating 

 the flower, which is our theme at this time. Often the flower is very- 

 irregular, the separate petals varying greatly in form. This peculiar 

 conformation, as Darwin explained years ago, has directly to do with 

 pollination and so interests us greatly in this discussion. 



Within the corolla are the stamens, the male equipment of the 

 flower. These maj^ be the same number as the petals when they are 

 opposite or alternate with them. There may be a great number as in 

 most rosaceous flowers. Each stamen has a stemlike stalk, often 

 threadlike, hence called the filament, and a head known as the anther. 

 The anther bears the male element, the pollen, a fine dust of varying 

 color, though more frequently yellow. Each pollen grain is a cell' and 

 corresponds to the sperm cell in animals. In the very axis of the 

 flower we find the pistil, usually only one but sometimes as many as 

 there are petals, and rarely, as in the strawberry, many. The pistil 

 is the female organ of the flower. Its bulbous base is knoAvn as the 

 ovary which bears a slender appendage, the style. The latter is tipped 

 with an unetious enlargement kno^vn as the stigma. In the ovary 

 grows the ovules — the plant eggs, if we may so speak — the female 

 elements of the plant. Like the pollen grain and the egg these are 

 cells which when fecudated by the pollen grain develop into the seeds. 

 The sticky, unetious stigma captures and. holds the pollen grains. From 

 each pollen grain there developes a thread which pushes down the 

 entire length of the style and enters an ovule. This is fecunda- 

 tion and is absolutely necessary to the formation of a seed. The seed 

 is the partially developed plant — an embryo — and as the animal egg 

 can not usually develop without the sperm cell, no more can this 



