238 Influence of Environment on Plants 
flowers by varying the time at which the stimulus is applied, and by 
the cooperation of other factors such as temperature, darkness, ete, 
In number and arrangement the several floral members vary within 
wide limits; sepals, petals, stamens, and carpels are altered in form and 
colour, a transformation of stamens to carpels and from carpels to 
stamens occurs in varying degrees. The majority of the deviations 
observed had not previously been seen either under natural con- 
ditions or in cultivation; they were first brought to light through the 
influence of external factors. 
Such transformations of flowers become apparent at a time, which 
is separated by about two months from the period at which the 
particular cause began to act. There is, therefore, no close con- 
nection between the appearance of the modifications and the external 
conditions which prevail at the moment. When we are ignorant of 
the causes which are operative so long before the results are seen, 
we gain the impression that such variations as occur are spontaneous 
or autonomous expressions of the inner nature of the plant. It is 
much more likely that, as in Sempervivum, they were originally 
produced by an external stimulus which had previously reached the 
sexual cells or the young embryo. In any case abnormalities of this 
kind appear to be of a special type as compared with ordinary 
fluctuating variations. Darwin pointed out this difference; Bateson! 
has attempted to make the distinction sharper, at the same time 
emphasising its importance in heredity. 
Bateson applies the term continuous to small variations connected 
with one another by transitional stages, while those which are more 
striking and characterised from the first by a certain completeness, 
he names discontinuous. He drew attention to a great difficulty 
which stands in the way of Lamarck’s hypothesis, as also of Darwin’s 
view. “According to both theories, specific diversity of form is 
consequent upon diversity of environment, and diversity of environ- 
ment is thus the ultimate measure of diversity of specific form. 
Here then we meet the difficulty that diverse environments often 
shade into each other insensibly and form a continuous series, 
whereas the Specific Forms of life which are subject to them on the 
whole form a Discontinuous Series.” This difficulty is, however, not 
of fundamental importance as well authenticated facts have been 
adduced showing that by alteration of the environment discontinuous 
variations, such as alterations in the number and form of members 
of a flower, may be produced. We can as yet no more explain 
how this happens than we can explain the existence of continuous 
variations. We can only assert that both kinds of variation arise in 
response to quantitative alterations in external conditions. The 
1 Bateson, Materials for the study of Variation, London, 1894, p. 5. 
