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. Westeate, Agronomist, and H. 8. Cor, Scientific Assistant, Office of Forage- 
Crop Investigations. 
In collaboration with A. T. Wrancxo and F. E. Ropsrnys, of the Indiana Agricultural 
Experiment Station, and H. D. Hueues, L. H. PaMuert, onal N. Martin, of the 
Towa Agricultural Doane Station. 
: CONTENTS. 
Page. Page. 
JETRO CHG ROMS Se = 3A SES oo aeacasesesne 1 | Cross-pollination and self-pellination of red 
Previous investigations on the pollination. of ClOVGI Es TREE hee ee Fa ES 11 
etal OMI ree ey ed eS ei eae 2 | Artificial manipulation of clover heads........ 12 
Outline of pollinating experiments... .....------ 5 | Bumblebees ascross-pollinators ofredclover.... 17 
Structure of the red-clover flower..---..-------- 5 | Honeybees as cross-pollinators ofred clover..... 18 
Length of the corolla tube of red-clover flowers. 7 | Mechanical cross-pollinators ofred clover.....-- 20 
Development of the flowers of red clover..---- TAGS UT an yee se to Soc a oO oe ee eee ee 26 
Fertilization of red-clover flowers. ..-..-.------ LO: dpiterature ciied=02+) ee eek eee ae 29 
Potency of pollen in self-pollination..........--- 10 | 
INTRODUCTION. 
For a number of years the quantity ef 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. _ , 
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, 289-151 : 
