SANIO’S LAWS FOR THE VARIATION IN SIZE OF 
CONIFEROUS TRACHEIDS 
IRVING W. BAILEY AND H. B. SHEPARD 
In 1872 SANtIo' published the results of an investigation upon 
the tracheids of Scotch pine, Pinus sylvestris L. From his observa- 
tions and measurements he deduced five general Jaws which may 
be translated as follows: 
1. In the stem and branches the tracheids everywhere increase 
in size from within outward, throughout a number of annual 
rings, until they have attained a definite size, which then remains 
constant for the following annual rings. 
2. The constant final size changes in the stem in such a manner 
that it constantly increases from below upward, reaches its maxi- 
mum at a definite height, and then diminishes toward the 
summit. 
3. The final size of the tracheids in the branches is less than in 
the stem, but is dependent on the latter, inasmuch as those branches 
which arise from the stem at a level where the tracheids are larger 
themselves have larger tracheids than those which arise at a level 
where the constant size is less. 
4. In the gnarled branches of the summit the constant size 
in the outer rings increases toward the apex, and then falls again, 
but here irregularities occur which may be absent in regularly 
grown branches. 
5. In the root the width of the elements first increases, then 
falls, and next rises to a constant figure. An increase in length also 
takes place, but could not be exactly determined. 
SANIO’S measurements and conclusions have been accepted 
by DeBary, PFEFFER, HABERLANDT, and others and have eis 
considered to be applicable to conifers in general. 
; art, Uber die Grisse der Holzzellen bei der gemeinen der Kiefer 
(Pinus inte Jahrb. Wiss. Bot. 8:401-420. 1872 
Botanical Gazette, vol. 60] [66 
