252 
were determined for a number of plants 
and tabulated. It was discovered that 
in Liriodendron tulipifera, Sanguinaria Cana- 
densis, Ailanthus glandulosus variations in the 
size and configuration of the leaves were in 
part due to the persistence of juvenile 
forms, to the arrested development of some 
leaves, and to their evolution and trans- 
formation to higher forms. The amount 
of these differences was ascertained, con- 
trasted and tabulated. In conclusion, it 
was stated that these changes are in most 
cases due to two causes, viz., the inter- 
nal hereditary impulse determining, as in 
Ailanthus glandulosus, the asymmetry of the 
lateral, paired, leaflets, and to the direct, 
environmental influence, fitting the leaf to 
utilize the space at its disposal, thus en- 
abling it to present the largest amount of 
leaf surface to light action. 
Critical Points in the Relation of Light to Plants: 
Proressor D.T. MacDouaar, New York 
Botanical Garden. 
The following statements, upon the basis 
of accepted facts, may be made as to the 
influence of light upon plants : 
1. Light exercises a direct chemical ef- 
fect upon the substances of which proto- 
plasm is composed. 
2. It stimulates protoplasm to the forma- 
tion of chlorophyll, although its action is 
not necessary to the process, and its direct 
chemical effect disintegrates this substance. 
3. It constitutes a source of energy, which 
is absorbed by the chlorplasts. 
4. Absence of light constitutes a specific 
stimulus, calling out the various reactions of 
etiolation. 
5. Light acts as a directive or orienting 
stimulus to which the plant responds by 
locomotory or bending movements. 
6. Different portions of the spectrum are 
operative in producing these separate ef- 
fects. 
If an examination is made of the facts 
SCIENCE. 
(N.S. Von. XIII. No. 320. 
upon which these generalizations rest, with 
reference to the current conceptions of 
phototonus, paratonic influence of light, maat- 
mum, ninimum and optimum, it will be found ; 
that illumination is not necessary to the 
motility of protoplasm, and conversely that 
deprivation of light does not induce a condi- 
tion of rigor, but sets up various patholog- 
ical phenomena, among which is the break- 
ing down of chlorophyll. 
Light does not exert a paratonic or re- 
tarding effect upon growth. Its chemical 
action may hinder the accumulation of 
somatic material however. The altered 
development of plants in darkness is an 
adaptive response which has for its purpose 
the elevation of the chlorophyll screen and 
reproductive bodies. 
Chemical, photosynthetic and phototropic 
maxima, minima and optima are so widely 
separated that phototonus as a term to des- 
ignate the condition of a plant when acted 
upon by light of an optimum intensity, or 
of an intensity between the maxima and 
minima, is useless and untenable, as are also 
light optimum, maximum and minimum 
when applied in generality to the light re- 
lations of the plant. 
Propagation of Lysimachia terrestris: PRo- 
Fessor D. T. MacDoueat, New York 
Botanical Garden. 
The development of the secondary and 
tertiary branches of the stems of Lysimachia 
terrestris is arrested by conditions unfavor- 
able to seed formation, and these branches 
assume the form of short cylindrical organs 
less than 1.5 cm. long without epidermal 
openings, and consisting of 3 to 5 internodes. 
The stele shows only protphloem and pro- 
toxylem. These bulbils fall to the ground 
and may survive under the cover of dead 
leaves to reproduce the plant in the next 
season. The bulbil completes its develop- 
ment as a rhizome and does not perish, as 
in most cases of bulbs and bulbils. Bul- 
