436 BOTANICAL GAZETTE [DECEMBER 
resembles the potato in the development of subterranean stem tubers. A tuber 
placed in an erect position, partially below the soil line and partially above it, 
develops roots and rhizomes from the buried portions and green shoots from 
the aerial portions. Instead of decaying rapidly, as a tuber commonly does 
when it has disposed of its stock of reserve food materials, the Oxalis tuber, 
placed in this abnormal position, lives and grows through the entire season. 
The tuber is obliged to function as a stem, bothin the conduction of water and 
the plastic foodstuffs and in giving mechanical support to the aerial organs. 
As a result of these new functions, the author finds a striking change in the 
anatomy of the tuber. Instead of the predominance of parenchymatous 
storage cells, there is a great increase in the area of the vascular bundles; 
the secondary phloem and xylem develop remarkably, and the new cells and 
cell fusions have a much larger cross section and more complicated structures. 
The strong development of bast fibers and wood cells materially adds to the 
mechanical strength of the tuber in its new relations. Thus the tuber has 
become like a normal stem in structure as in function. 
The suppression of normal tuber formation in Oxalis stimulates their 
development in a new position. The plant sometimes develops stolons 
whose ends bury in the soil and develop tubers from the terminal bud. If this 
bud is removed, the bud nearest the end becomes a tuber, and if all the buds 
are removed one of the stolon internodes swells up like a tuber. In some 
cases the leaves instead of the internodes become tubers, and the leaflets 
may remain as rudiments or may swell up like the petiole. The structure of 
the petiole which functions as a tuber undergoes a remarkable change. The 
ventral furrow is absent, the petiole being round in cross section. There is 
no collenchyma, or green tissue, and the bundles which are so prominent in a 
normal petiole remain in a rudimentary condition; even the vessels which 
are present may be filled up with tyloses. The changed petiole is almost 
assume the most fantastic shapes ; indeed Vichting commonly finds that the 
more abnormal the organ which becomes a tuber, the more abnormal are the 
starch grains, indicating an intimate correlation of structures of a surprising 
nature. 
Experiments similar to those just mentioned were performed on the 
potato but were less successful as a rule, showing, the author thinks, that 
Solanum is less plastic and that the metamorphosis of stem to tuber has gone 
further than in Oxalis. A root of Dahlia variabilis was planted somewhat 
emerging from the soil. The new roots, which commonly form in a cluster 
at the base of the stem, formed at the base of the parent root, since the base 
of the stem was inthe light. The next year the compound root system was 
planted with these new roots emerging from the soil, and new roots formed at 
the base of this second story of roots. This process was repeated until 
