Productiveness and Degeneracy of the Irish Potato 7 
or its tuber to dry rot. The quality is excellent under good conditions. 
Those regions which find Pearls their best variety are unable 
to maintain Pearl yield or shape, and are compelled to buy seed from 
other regions every year for raising the seed tubers to plant the large 
fields for the following year. Greeley also finds the Pearl variety 
subject to knots. In fact the most pressing economic need for the 
potato industry of Colorado is the increase and betterment of the 
Pearl seed supply. 
Pearl Vines, Tubers and Blossoms .—The most productive Pearl 
vine (No. 1, Plate III.) stands, not erect in any of its parts, nor yet 
prostrate, and is typical of good conditions and good yields of tubers, 
free from knots and from deep or compound eyes. Where subjected 
to early drouth and close deep cultivation (No. 2) and then given 
abundant moisture, the main stems grow longer and interfere with the 
running of water as they become prostrate from the weight of “risers” 
which grow straight up from the nodes. The tubers produced by 
this common type of vine, while usually good, have deeper eye pits 
PLATE IV. COMMERCIAL PEARL SEED. 
1. 2. 3. 4. 5. 
Good Fair Intermediate Pearl Shaped Pear Shaped 
Bastard Bastard 
and more bulging eyes, and are subject to knots. About September 
1st good fields of No. 2 look like alfalfa fields, the growth is so rank 
and the surface of the field so even. Such a field is shown in the 
photograph, behind the irrigator, with a single No. 3 vine in front of 
the coat. Plate VI.,page 2. 
This type (No. 3) marks the change from value to worthlessness. 
Fields that are rough and ragged over the top from the presence 
of No. 3 and No. 4 are undesirable as a source of seed. These vines 
are much alike, except that No. 3 divides the top. The blossom of 
No. 4 is more developed, and its tuber shows sudden and great degen- 
