346 
Keport of the Botanist of the 
side of stems living for more than one year. In the potato tuber 
(which is an underground stem) the lenticels are scattered without 
order over the surface and are less than a pinhead in diameter. They 
are not conspicuous in the stored tubers, but in young or freshly dug 
tubers they are Usually easily seen, especially if permitted to swell 
up by being placed in water for a day or more. Lenticels have a corky 
texture, but the cells are rounded and permit the passage of air 
between them. Figure 2 shows a vertical section from the skin of a 
young potato (one inch in diam- 
eter), passing through a lenticeh 
Before making the section the 
skin was entirely separated from 
the other tissues of the tuber by 
Pi GUEB 2 masceration, thus exhibiting 
Transverse section of the skin of a more clearly the exact thickness 
young potato, cutting through a lenticel.- <? ■■■ • n * + i ^ 
Magnified 85 diameters. Original. ot the skin and the nature ot the 
break in continuity made by the lenticel. 
Ten years before Dr. Nobbe made the remark quoted above, a 
careful account of the scab — its appearance, microscopic structure 
and origin, together with the conditions favoring its growth — was 
given with fine illustrations in a report on investigations undertaken 
for the Prussian government by Dr. Schacht.* He pointed out that 
the conditions favoring the excessive growth of the lenticels also help 
to carry this growth over into the form of scab, and that marl, bog 
iron and street sweepings applied to the soil are supposed to have 
something to do with the increase of the trouble, and adds: "I must 
consider great moisture of the soil as the first cause." Little substan- 
tial addition has been made^o our knowledge of the subject since the 
time of Schacht. f The latest and most complete account is by 
SorauerJ in his new handbook of plant diseases. 
The experiments undertaken by the Station this season to test some 
points in connection with the question of scab have been in charge of 
Mr. M. H. Beckwith, the assistant horticulturist, and a full account of 
them will be found in his report in this volume. There were four 
points aimed at, as follows: To test the influence upon the crop (1) of 
the use of scabbed potatoes for planting, (2) of the application of 
fungicides and special fertilizers, (3) of the degree of moisture in the 
* Bericht iiber die Kartoffelpflanze und deren Krankheiten, 1854, p. 24. 
t His report furnishes the basis of what is given in the Kep. Conn. Agric 
Exper. Station, 1877, p. 67, and L886, p. 79. 
t Pflanzenkrankheiten, 2te Aufl.., ISS6, p. 227. 
