1911] OVERTON—TRANSPIRATION AND SAP-FLOW 31 
physical and partly vital, and the vital factor is eliminated by 
killing a portion of the stem. 
URSPRUNG (34) has also used ether, induction currents, and low 
temperature to kill portions of the stems of both cut and rooted 
plants. By removing half of the cortex for 10 cm. from the branches 
of Fagus and exposing the wound to ether, the leaves were observed 
to wither in 2-3 days. By cooling portions of the branches of the 
same species with ice for 12-30 cm., the leaves above were always 
observed to wilt in 2-6 days, depending on the length of the cooled 
portion. All of these researches cause URSPRUNG to conclude that 
the living cells are in some way essential to the ascent of water. 
STRASBURGER also performed some experiments on plants in 
connection with the roots, killing various stretches of the stem 
with heat. UrsprunG (32, 33) in discussing these experiments 
notes that the leaves above fade, and concludes that the water 
does not pass through the killed portion in sufficient quantities 
to supply the leaves. He thinks, therefore, that STRASBURGER’S 
_ experiments show that the living cells of the stem are necessary 
in order that a sufficient amount of water may ascend to supply the 
leaves. He further cites in favor of his own view the experiments 
of Boru (3), in which 18 cm. of stems of bean plants were killed 
with steam, noting that the leaves above ‘‘lived”’ for a period not 
longer than 3 weeks; wilting usually occurred sooner. BorHM 
considered that the wilting was due to a plugging of the vessels 
with mucilage or to a severing of the water columns. URSPRUNG 
passes over this observation with the remark that it teaches 
nothing new. : 
Considering the possibility of the participation of the living 
cells of the stem of a plant in sap-flow, Drxon (9) has repeated 
some of the experiments of URSPRUNG (32) with rooted stems and 
attached leaves. Although he fully supports UrsprtNe’s account, 
he gives quite a different interpretation of the results obtained. 
_ When only “short lengths” of the stems of Primula, Chrysan- 
~ themum, Syringa, Philadelphus, and Cytisus were killed by heat, 
_ the leaves beyond ‘“‘scarcely suffered,” little injury appearing; 
but when 2-5 cm. lengths were killed, the leaves showed injury 
in proportion as the length of the killed region was increased. 
