Irrk;ation Water 
21 
ear mustard (Conrhujla orienlalis), Prenchweed (Thlaspi ar- 
vense), broad-leaved plantain (Planiago major), and ShephercPs 
purse (Capsella bursa-pastoris), are heavier than water and sink 
immediately if agitated. Such seeds would not be carried 
long distances except in very swiftly running water. 
If some seeds alight gently on the surface of water, and the 
water surface is undisturbed, as in the case of a slowly running 
stream, the seeds will float for a long time, but if the surface 
is agitated, as it would be in the case of a swiftly running 
stream, the seeds readily sink. See Table V.) 
BUOYANCY OF WEED SEEDS 
Some weed seeds float for an indefinite period if laid care- 
fully upon a smooth water surface, and the surface is not dis- 
turbed (See Table IV). However, many of the same species of 
seeds sink if they fall on the surface from a short distance 
above the water. The following experiment in which seeds 
were dropped from a height of 5 feet upon a water surface 
was intended to simulate the situation along ditch banks 
where the seeds fall from weeds over-hanging the water* 
TABLE VI. — BUOYANCY OF 
SEED — WHEN DROPPED 
INTO WATER 
FROM 
A HEIGHT OF 5 FEET THRU A 1 / 2 ' 
' GLASS TUBE 
INTO A 250 C. C 
BEAKER — 100 
SEEDS 
OF 
EACH SPECIES USED 
Kind of Seed — 
Floated 
Sank 
Echinochloa crus-galli 
100 
0 
Rumex crispus (hulled) 
33 
67 
Rumex crispus (unhulled) . . . 
100 
0 
Amaranthus graecizans 
23 
77 
Sisymbrium altissimum 
39 
61 
Solanum triflorum 
50 
50 
inr*i.C!Q 
76 
24 
Abutilon abutilon 
28 
72 
Onagra strigosa 
100 
0 
P*r>7’tiil n r»n nlprapcn . . 
28 
72 
f-Tynpyamns ■nig’pv 
100 
0 
Cuscuta planiflora 
52 
48 
T'^^lium t<^m 1 1 11 m 
64 
36 
Capsella bursa-pastoris 
70 
30 
Polygonum convolvulus 
87 
13 
Carduus arvensis 
96 
4 
Brassica arvensis 
30 
70 
Ple.ntago lanceolata 
30 
70 
Thlaspi arvense 
30 
70 
