Nature and Cause of the Potato Disease. 
301 
advanced, and the plant has arrived at a state in which it could 
exist if the parent set were taken from it. 
The stolons spring alternately from the footstalk, and in oppo- 
site directions to each other, and at their commencement grow 
upwards for a few inches, generally at an angle of from 18° to 20° 
with the stem. Each stolon has 4 main roots, see plate 3, fig. 3 ; 
these roots accompany the stolon and spread themselves out hori- 
zontally and at right angles with the footstalk. Two of the main 
roots spring from the base of the stolon at its j uncture with the 
stem, and two at the superior part where the lines meet that from 
the apex of the angle. The main roots have numerous lateral 
ones, which again have their laterals. Each fibre is terminated 
by a sponglole, or mouth for absorbing water and inorganic matter 
from the soil. In a young plant, such as plate 3 represents, I 
carefully measured and counted the roots in order to ascertain 
the number of absorbents and the length of the roots as well. 
The plant thus examined was a mere germ, and not advanced 
beyond what the plate represents. It had 6 stolons and 24 main 
roots. The length of these roots varied from 9 to 12 inches, 
giving rather more than 10 inches as the mean length of each 
root. The lateral roots springing from the main roots varied from 
1 to 3 inches in length, and averaged 10 to every inch of the 
main roots. Taking the mean length of the laterals at 2 inches 
and their number at 10, we have 4800 inches, or 400 feet for 
the length of roots in a young plant barely more than a germ. 
To the roots of this plant there would be 2424 distinct mouths 
or absorbents for feeding the plant, a number apparently great, 
considering its size. But great as this extent of roots and number 
of spongioles in the young plant may appear, it is only a fraction 
of what exists in a full-grown one. In a healthy plant of the 
shaw kind in a state of maturity there is at least 10 sets of main 
roots with 4 to each set. The length of the main fibres average 
12 inches each, the laterals 10 to every inch, with a mean length 
of 4 inches for every lateral. Assuming these data correct, we 
have 19,200 inches, or nearly one-third of a mile for the length 
of the roots of a potato plant when at maturity. The number of 
mouths or absorbents to this extent of roots is very considerable ; 
for the main roots and all the laterals terminate in spongiole, and 
as new filaments appear, so do absorbents also appear with them ; 
consequently the length of roots and number of mouths are in- 
creasing with the growth of the plant until nature has exhausted 
her powers by a completion of the products the plant was destined 
to form. Calculating, therefore, at a low average, the number 
of mouths in each lateral of 3 inches' length at 5, and taking the 
number and extent of the roots as already shown, we have 24,000 
absorbents for the whole plant, which, while in health, are 
Y 2 
