66 TENOPYR: CONSTANCY OF CELL SHAPE 
Neither in the case of Campanula nor the other plants studied 
did I find the size of the individual cells to be as constant as Ame- 
lung’s measurements would indicate. Because of the wide range 
of variation in cell size, the average cell size could be determined 
only through numerous counts. Usually one hundred counts 
were made on each form of leaf, so that the average cell size given 
is the average size of from six hundred to seven hundred cells. 
LoBELIA ERINUS 
This plant, like Campanula rotundifolia, has three distinct 
forms of leaves. The orbicular radical leaves are developed before 
the flower shoots appear, and are rarely found at the time of 
flowering. The slender, somewhat recumbent shoots bear at first 
only spatulate or obovate leaves, but later, as the stem elongates, 
it has small linear leaves near its summit. The flowers grow from 
the axils of these linear leaves. Each type of leaf produced is not 
only smaller than the one which preceded it but it is also propor- 
tionately narrower. 
A comparative study was made of the shape st the cells of the 
lower epidermis of the three forms of leaves, in relation to the 
shape of the whole leaf. Only those linear leaves were examined 
in whose axils the flowers had already faded, as I thought these 
leaves were probably fully grown. Measurements were made on 
six such leaves after two intervals of two weeks each, to see if 
they had ceased to grow by the time the flowers had bloomed. 
There was some further growth, but scarcely enough to seriously 
affect the proportions of the leaf, or noticeably alter its shape 
(TABLE III). 
TABLE III 
LoBeELIA ERINUS 
Record of further growth of linear leaves, after flowers in their axils had faded. Line 
of measurement = 
Plant A B c pcb pd se 
| Length eit: a Length Length| Length 
| width width width wk} eta | wih 
First ca ag | 10 % 25 ¢ 36: FT te a ae 142 119 X S| 190 X4 
End second week.....| 10 X 1.87) 11 X 1.5| 12 X 2.5/15 X2.5| — 20 X 4 
End fourth week... ../11.5 X 1.87! 11 X 1.5 Died 16 X 2.5 121 X 9\20.5 X 4 
