TENOPYR: CONSTANCY OF CELL SHAPE 55 
Similarly, Keeble (1912), ina comparative study of the cells of 
the stem and leaf tissues of White Queen Star, a horticultural 
variety of Primula sinensis, and those of its mutant, Giant White 
Queen Star, showed that the latter is a giant because its cells are 
larger and not because they are more numerous than those of the 
parental type. Indeed, in the cortex of Giant White Queen Star, 
Keeble found fewer cell layers than in the normal type. The meas- 
urements he gives for the cortical cells of the flower peduncles, taken 
for the layer immediately external to the endodermis, are: 
Radial measurements..........:..5.... g:m:: 100: 48 
Tangential measurements.............. £2 :- 100; BI 
Longitudinal measurements............ £72 032: 1002 S97 
The cells are larger in all three dimensions, radial, tangential 
and longitudinal, and the gigantism is common to all tissues. He 
does not state how many cells were measured nor does he describe 
his methods. The chromosome number in both varieties is the - 
same. The nuclei of the giant form are larger, as Keeble shows in 
his drawings of pollen grains, but he does not give any measure- 
ments of them. It is therefore impossible to tell, in the case of 
White Queen Star and its giant mutant, Giant White Queen Star, 
whether or not the amount of chromatin material is the factor de- 
termining the relative cell size in these plants. 
In Avena sativa, Jakushkine and Wawilow (1913) found that 
different varieties may have different-sized cells, but they were 
unable to discover any relation between the size of either the 
stomata or the epidermal cells, and that of the leaf surface, when 
varieties with different-sized organs were compared. For in- 
stance, a small-celled variety had the largest leaves. Like Sanio 
these authors found that the cell size of the leaves varied according 
to their position on the stem, the cells of the highest leaf being 
smaller than those of the third leaf from the topof the stem. They 
- found that in any given variety, the cell size of any tissue at a 
definite part of an organ was a constant character, and further 
that each of the seventeen pure lines obtained through selection 
from a mixed population of German and west Russian oats, fell 
into one of two groups, namely: 
1. A large-celled group, the average length of the stomata of 
the highest leaf being 0.063 mm., that of the third leaf down being 
0.0735 mm. 
‘ 
