UNITED STATES DEPARTMENT OF AGRICULTURE 



BULLETIN No. 289 



Contribution from the Bureau of Plant Industry 

 WM. A. TAYLOR, Chief 



Washington, D. C. 



PROFESSIONAL PAPER 



September 21, 1915 



RED-CLOVER SEED PRODUCTION: POLLINATION 



STUDIES. 



By J. M. Westgate, Agronomist, and H. S. Coe, Scientific Assistant, Office of Forage- 

 Crop Investigations. 



In collaboration with A. T. Wiancko and F. E. Robbins, of the Indiana Agricultural 

 Experiment Station, and H. D. Hughes, L. H. Pammel, and J. N. Martin, of the 

 Iowa Agricultural Experiment Station. 



CONTENTS. 



Page. 



Introduction 1 



Previous investigations on the pollination of 



red clover 2 



Outline of pollinating experiments 5 



Structure of the red-clover flower 5 



Length of the corolla tube of red-clover flowers. 7 



Development of the flowers of red clover 7 



Fertilization of red-clover flowers 10 



Potency of pollen in self-pollination 10 



Page. 

 Cross-pollination and self-pollination of red 



clover ii 



Artificial manipulation of clover heads 12 



Bumblebees as cross-pollinators of red clover 17 



Honeybees as cross-pollinators of red clover 18 



Mechanical cross-pollinators of red clover 20 



Summary 26 



Literature cited 29 



INTRODUCTION. 



For a number of years the quantity of seed of red clover ( Trifolium 

 pratense) produced in this country has been insufficient to supply the 

 demand for reseeding purposes in the clover-belt States. This not 

 only has caused the seed to be high in price, but has resulted in the 

 importation of large quantities of foreign seed, some of which, on 

 account of the impurities present and its low vitality, has been 

 considerably less desirable than the ordinary^home-grown strains, v ( 



The prime importance of clover in the ordinary farm rotations in 

 the corn and clover belt States makes the continued maintenance of 

 the clover acreage of great moment to the agricultural prosperity of 

 the country. This problem has been approached from four different 

 angles. First, to determine the minimum amount of seed necessary 

 to obtain a stand, so that much less than the quantity of seed ordi- 

 narily sown will be sufficient to produce a satisfactory yield, for any 



2990°— Bull. 2S9— 15 1 



