10 BULLETIN 75, U. S. DEPARTMENT OF AGRICULTURE. 
RELATION OF TRIPPING TO THE DEVELOPMENT OF SEED. 
In order to obtain more abundant data in regard to the relation 
of tripping to the production of pods and seeds, the experiment here 
described was conducted: 
On selected plants, approximately two-thirds of the branches were 
inclosed in fine-meshed mosquito-bar tents to prevent insects from 
having access to the flowers. Tarlatan was the material used for 
the netting. The meshes averaged 25 to the linear inch, thus being 
from one-half to one-third finer meshed than ordinary mosquito 
bar, which was thought to be too coarse to exclude the smaller insects 
which might gain access. The remaining stems of each plant were 
left outside the tent, where the flowers could develop under natural 
conditions. On both portions of the plant a number of racemes were 
marked, each with a tag, and numbered. AI! unopened flower buds 
and all wilted or tripped flowers were cut off from each of these 
racemes, leaving only the fresh, open, and untripped flowers. The 
flowers on approximately one-half of the marked racemes inside the 
netting were artificially tripped. This was done usually by means of 
a slender alfalfa stem or grass stem, pushed down between the keel 
and the standard. On some of the plants used in this experiment, a 
separate stem was used for each flower, so as to exclude pollen from 
other flowers, while on other plants the same stem was used to trip 
several flowers on the same plant. The flowers were fertilized in all 
cases, therefore, with poilen from the same flower or with pollen of 
other flowers on the same plant. The flowers on the remaining 
racemes inside of the netting tent were allowed to develop without 
being tripped through the visit of insects or by any artificial agency. 
This experiment was carried out at Pullman, Wash., in 1908, 1909, © 
and 1910; at Chico, Cal., in 1908 and 1909; at Arlington farm, Vir- 
ginia, in 1908; at Chinook and Havre, Mont., in 1909; and at New 
London, Ohio, in 1912. The summarized results are shown in 
Table II. 
TaBLE II.—Pods and seeds produced by alfalfa flowers on the same plants, free and pro- 
tected from insects. 
A.—OUTSIDE NETTING: FLOWERS DEVELOPED UNDER NATURAL CONDITIONS. 
Total Total lowers Average 
Wear elace Number | number | Number | number pearing number 
5 F of plants. of of pods. of nds of seeds 
flowers. seeds. pods. | per pod 
Per cent 
LG Seis. s se see ee oe IRullimank pees ee 7 633 155 426 24 2. 74 
Chico tees eeaeeee 15 3, 474 321 681 9. 24 Qe 
ATLITICLOM sae eS soot ee 1 80 35 31 43. 75 - 88 
OOD Bieta aie sella Paliman eens oss 15 1, 468 480 1, 730 32. 69 3. 60 
@hinook: 233-52 25.2 o- 10 4 143 320 15.14 2. 23 
LA VIO! os sisecie ere = cere 9 366 a We [ae See 135950| 425052 ces 
Chicosehestae ess -c% 8 1, 589 220 Ne eine seer ey ol Re ere 
NOLO Sete ct sete cise oar Bullman ee. ey. a 6 228 30 38 13.15 1.26 
LORD ae Vos cette New London........ 6 157 56 105 35. 66 1.80 
WOVE ERS Roe at seo ao 77 8,939 |) 1 aOOsSoiant Sonal omer ye me = = eee 
IAVOTAL Css aise omc ne asics ciominesi sia crallem  acmreieare Paaeecryte Famcae os | ees 16. 76 2. 22 

