Bui . 844, U. S. Dept. of Agriculture 
.a ~\ 
PLATE V. 
Vm 
i 
^." 
yS^*H 
~~s=^ 
^BLj 
FifY 5 
=Jte 
^Jf? 
l-.iJ. 
n 
ra ¥. 
I 
%£ 
i'^v ', 
/<? 
Structure of the Seed Coat of Sweet Clover. 
Fig. 1.— Section of the seed coat of Melilotus officinalis. X450. Fig. 2.— Another section of the seed 
coat of Melilotus officinalis, showing the variation in size and modifications that occur in the three 
layers. X450. Fig. 3. — Section of the Malpighian layer of a Melilotus alba seed, showing a line of 
canals just above the light zone. X450. Fig. 4.— Section of the Malpighian layer of a permeable 
Melilotus alba seed. X450. Fig. 5.— Tangential section of the Malpighian cells cut between the 
cuticle and tops of the cones, showing pores. X530. Fig. 6.— Section through the Malpighian layer 
of an impermeable Melilotus alba seed. X450. Fig. 7.— Section through the Malpighian layer of an 
impermeable Melilotus alba seed, showing the region through which water and stains readily passed. 
X-450. Fig. 8. — Cross section of a Malpighian cell of a permeable Melilotus alba seed through the 
region of the light zone, showing the lumen not entirelv closed. X530. Fig. 9.— Section through the 
Malpighian layer of a Melilotus alba seed shaded to show the portions which react to the cellulose and 
pectose tests. X450. Fig. 10.— Section through the Malpighian layer of a Melilotus alba seed which 
shows the condition of the seed coat after 60 minutes' treatment of concentrated sulphuric acid. That 
portion above the light zone was destroyed, and the lnmina as small pores through which much of 
the stain now passed were seen extending across the light line. The lines between the cells were 
much more distinct , appearing as small intercellular spaces through which some stain passed. X450. 
a, Cuticle; b, cuticularized layer; c, conelike portion of the thickening of the Malpighian cells; d, 
light line; e , region of a hard seed coat through which water and stains readily passed; I, lumen; M, 
Malpighian cells; N, nutrient cells; O, osteosclerid cells; p, canals just above light zone. 
