588 PROF. D. T. MACDOUGAL ON THE GROWTH OF 
Lilium tigrinum, Ker. 
Young plants with small scaly bulbs, known to the gardener 
as “ 8rd size," were obtained, but only in such limited quantity 
that but few experiments were carried out. 
Effect of an Atmosphere free from CO,.—Entire plants placed 
in the apparatus were able to form perfect leaves. The death of 
the older leaves near the base of the stems occurred in the same 
manner as in normal plants. A general resemblance appears 
between the behaviour of this species and Trillium. 
Zea Mays, Linn. 
Seedlings were grown from selected grains placed in small pots 
of earth in the usual manner. 
Effect of an Atmosphere free from CO,.—Seedlings with the 
shoot emerging from the cotyledon were placed entirely inside 
the apparatus, where they remained for a period of from 8 to 12 
days. In such experiments, the plant evidently could carry on the 
extension of the shoot and leaves only so long as food could be 
obtained from the seedling. To determine the actual constructive 
value of the stored food in the seed, plants were allowed to 
remain in the apparatus until the leaves exhibited indications of 
deterioration, which was from 11 to 14 days after the beginning 
oftheexperiment. The plants were more slender and the leaves 
narrower than in control plants. A small amount of starch was 
still to be observed in the seeds, both in the plants grown in the 
air free from CO, and in normally grown plants of the same age 
(see Plate XIX. figs. 5, 6). 
Effect of Darkness.—In darkness the stems are elongated and 
the etiolated leaves are much narrower than in normal plants. 
Phenix dactylifera, Linn. 
Specimens were obtained by the germination of the seeds of 
the commercial fruit, a process requiring from 20 to 30 days. 
The seed consists largely of reserve cellulose, and, according to 
Haberlandt, it is sufficient to allow the tormation of a primary 
root more than a metre in length before the unfolding of the 
first foliage-leaf, in the natural habitat of the plant. In my 
experiments the planting of the seeds in moist soil made this 
excessive development of the root useless, and foliage-leaves 
began to unfold when the root had attained a length of a few 
centimetres. 
