834 
Journal of Agricultural Research voi. xxvii,no. n 
which numerous groups of phloem are embedded, though procambial in 
origin, appears distinct from the vascular ring and is not the result of 
cambial growth. 
(2) The morphological advantage which the apical eye possesses over 
the basal ones seems to offer the most reasonable explanation for the 
dominance of the former. 
(3) The nucleus of the sieve tubes disappears before the elements 
fully matured. The peculiar protozoan-like structures observed in have 
young sieve tubes are of cytoplasmic origin and have only a temporary 
existence. 
(4) In a consideration of the chemical constitution of the tuber, the 
protein crystals, the tannin vesicles, and the solanin are of special interest. 
The protein crystals occur abundantly in the peripheral cells of the cortex; 
the tannin vesicles in the region of the buds, especially at the time of 
sprouting; the solanin accumulates in large quantities in the region of the 
buds, where it appears to be of importance in the metabolism of the 
growing plant. If germination is held back, solanin may accumulate in 
abnormal quantities. 
(5) The phloem of the stolon occupies about 24 per cent of the area of 
the stolon cross section. Its extensive development, in response to the 
apparent need for increased food movement, strengthens the view that 
the phloem is, after all, the most important channel for the translocation 
of organic substances. 
(6) A study of such internal characters as might aid in the task of 
grouping potato varieties or establishing their relationship indicates that 
the presence or absence of stone cells is the only definite character which 
can be used successfully in a classification scheme. 
LITERATURE CITED 
(1) Appel, Otto. 
1906. ZUR KENNTNIS DES WUNDVERSCHLUSSES BEI DEN KARTOFFELN. In Ber. 
Deut. Bot. Gesell., Bd. 24, p. 118-122, pi. 9. 
(2) Brehmer, W. VON. 
1921. DAS SOLANIN in DER kartoFFELPFlanze. In Mitt. Biol. Reichsanst. 
Land. u. Forstw., Heft 21, p. 269-273, fig. 50-51. 
(3) Dixon, Henry H. 
1922. TRANSPORT OF ORGANIC SUBSTANCES IN PLANTS. In Nature, V. IIO, p. 
547 - 55 1 - 
(4) Edson, H. A., and Shapovalov, M. 
1919. wound-cork formation in the potato in relation to seed-piece 
decay. In Phytopathology, v. 9, p. 483-496, illus. Literature cited, 
p. 495-496. 
(5) Esmarch, F. 
1919. BEITRAGB ZUR ANATOMIE DER GESUNDBN UND KRANKEN KARTOFFEL¬ 
PFLANZE. In Landw. Jahrb., Bd. 54, p. 161-266, 267-276, illus. 
(6) Franz, Hermann. 
1873. studibn an der kartoffelknollb. In Jour. Landw., Jahrg. 21, p. 
306-360, pi. 1-3. 
(7) Kreitz, Wilhelm. 
1908. UNTERSUCHUNGEN ObER DIE SCHALB VERSCHIEDBNER KARTOFFBLSOR- 
• ten. In Arb. K. Biol. Anst. Land. u. Forstw., Bd. 6, p. 2-27. pi. 1-2. 
(8) Lutman, B. F. 
1919. resistance of potato tubers To scab. In Vermont Agr. Exp. Sta. 
Bui. 215, 30 p., 5 pi. 
(9) Mrazek, August. 
1910. fJBER GEFORMTE BIWEISSARTIGB INHALTSKCJRPBR BEI DEN LEGUMINOSEN. 
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