The Development of 4 Sanio’s Bars ’ in Pinus Inops. 
BY 
W. RUSHTON, A.R.C.Sc., D.I.C., 
Lecturer in Biology , St. Mary’s Hospital Medical School. 
With four Figures in the Text. 
T HE 4 bars of Sanio ’ are the short rods or bars found stretching, in 
most cases, from the two tangential walls of the tracheides, cambial 
cells, and phloem elements, in many Conifers and protruding as small rod- 
like projections into the lumen of the tracheides in the veins of the leaves 
of Juniper us. In many cases the bars in the wood of Conifers occur as 
a series of radial rods extending throughout several annual rings. In the 
xylem region these bars have lignified walls, and in the cambium and 
phloem walls of cellulose. 
The history of their investigation dates back to Sanio (1), and reference 
to them is occasionally found in the works of later investigators down to 
the present time. Sanio in his work records what he termed at first a false 
cell-wall crossing the cell cavities of the tracheides in Hippophae rhamnoides 
and in Pinus sylvestris. In radial section these appear as rods crossing 
from the inner to outer walls, and in tangential section as spots on the 
tracheide walls. Sanio regarded these at first as possibly being the end 
walls of tracheides, but abandoned this idea later. He further stated that 
in radial sections of wood the bars sometimes appear as little sprouts on 
each tangential wall of the tracheides. Sanio’s suggestion as to the origin 
of the bars is that they arise by a bending in of the two tangential walls of 
the tracheides, but he failed to find a corresponding depression of the outer 
contour of the tracheide, and further suggested that this may be due to 
some optical effect caused by some chemical alteration of the tracheide wall 
at that point. It was Sanio who first demonstrated that in the xylem 
region the walls are lignified and in other regions cellulose. 1 
Independent of Sanio, von Mohl (2), on investigating the leaf structure 
of Sciadopitys , found bars present in the vascular elements, and further 
1 Confusion was introduced as to these bars by Miss Gerry (Ann. Bot., 1902), by reference to 
the clear areas above and below the bordered pits of coniferous wood as being the ‘ bars of Sanio 
and further by stating these bars were of a cellulose nature. 
[Annals of Botany, Vol. XXX. No. CXIX. July, 1916.] 
