96 Nebraska Agricultural Exp. Station , Research Bui . 00 
HISTOLOGICAL EFFECTS OF INBREEDING 
The hybridization of elemental strains of corn is so com- 
monly attended with marked increase in plant size that it be- 
comes a matter of interest to know how this is related to cell 
development — the cell being the unit of plant structure. 
The data in Table 38, showing the relative number and size 
of certain histological units, covers seven pure lines and ten F T 
hybrids in which all seven pure lines are represented. Histo- 
logical material was gathered from four representative plants 
of each pure line or hybrid at about the silking period. The 
corn had attained its full vegetative development by this time. 
Material for stalk sectioning was taken midway of the first 
internode above the ground. Material for leaf study was taken at 
the widest portion of the main ear leaf midway between the mid- 
rib and the margin. In order to overcome the great variability 
among the different units, a large number of individual counts 
and measurements were taken for each strain. In the case of 
stalk sections, fifty independent observations were made for each 
character under consideration. In case of leaf measurements, 
this number was increased to 100. All of these microscopic ob- 
servations were made with unstained material preserved in 
alcohol. 
The data as taken are considered as indicative of the histo- 
logical differences which occur between pure lines and their 
hybrids. Plant individuality and limited amount of material 
may account for some of the irregularity and apparent incon- 
sistencies which occur in a few instances. These are probably 
fairly well eliminated in the averages for all the pure lines as 
opposed to the averages for all the hybrids. 
Comparing the hybrid with the average of its two parents, 
(1) the stalk diameter was 46 per cent greater, (2) the total 
number of fibrovascular bundles in a cross section of the stalk 
was 45 per cent greater, (3) the number of vascular bundles in 
one square centimenter of cross section of the stalk was 34 per 
cent less, which indicates that they are larger in size, (4) the 
number of bundles occurring along one diameter of a cross 
section of stalk was 21 per cent greater, (5) the number of bun- 
dles along one centimeter of the stalk diameter was 19 per cent 
less, (6) the actual diameter of vascular bundles was 15 per 
cent greater, (7) the number of pith cells along one diameter of 
cross section was 38 per cent greater, (8) the average diameter 
of one pith cell in stalk was 8 per cent greater, (9) the length 
of pith cells in the stalk was 10 per cent greater, (10) the leaf 
