536. PROF. D. T. MACDOUGAL ON THE GROWTH OF 
perfectly natural aspect. Mature leaves gave no indication of 
deterioration during the above period. 
Effect of Darkness—In darkness tbe leaf- and flower-stalks 
elongated rapidly, but when they reached a length slightly in 
excess of the normal began to deteriorate and soon died. The 
lamine and the floral envelopes were imperfectly developed. 
Removal of concurrent Members.—The removal of younger or 
older stems or of leaf- or flower-stalks in no wise affected the 
development of the remaining organs. 
Comment.—Isopyrum resembles Oxalis in that it is able to 
carry on the formation of perfect leaves in the sunlight in an 
atmosphere free from CO, so long as stored food-material is 
available. The existence of chlorophyll in this plant is inde- 
pendent of its functional activity. 
Calla palustris, Linn. 
This plant consists of a creeping rhizome 1 to 2 em. in thick- 
ness, from the apex of which arise a few cordate leaves with 
petioles 15 to 20 em. long, and one or more solitary scapes 8 to 
15 cm. high. The relatively large rhizomes are filled with 
stored food. 
Effect of an Atmosphere free from CO,.— Plants brought into à 
warm house and placed under the apparatus described above ex- 
hibited a development of the petioles and laminz during a period 
of from 10 to 12 days that resulted in the formation of perfect 
leaves. During this period the mature leaves offered no signs of 
deterioration. The continued existence of the plant, however, 
under such conditions was impossible, because of the destruction 
of the stored food by fermentation. In this particular a resem- 
blance to Trillium is exhibited. 
Effect of Darkness.—In the dark chamber a slight extension 
of the petioles occurred, while the laminz attained a size equal to 
those in the open air, although they were recurved at the margins. 
No effects were obtained by the removal of the concurrent 
members. 
Comment.— The most noteworthy feature in the experimental 
results obtained from Calla is that of the attainment of full size 
by the laminz of leaves grown in darkness. 
