420 
Rushton . — The Development of 
records bars occurring in the xylem of the leaves of Juniper us communis , 
J. Oxycedrus , J. oblonga , and J. macropoda, but in this case mostly occurring 
as projections which end blindly in the lumen of the tracheide. 
About the same time C. Winkler ( 3 ) recorded the occurrence of bars 
in Araucaria brasiliensis. 
The following year Russow ( 4 ) observed Sanio’s bars in the wood of 
tracheides of Abies Pichta and Finns sylvestris, and found them crossing 
ten successive annual rings and passing through the cambium and young 
bast elements : he further records their presence in Pinus nigra> P. Pine a , 
P, Strobus , P. Laricio, and P. anachuite . 
Mention is also made of rod-like outgrowths by de Bary ( 5 ), under the 
head of ‘ Tracheides with Transverse Bars’, who records them as occupying 
the corners of the vascular bundles of the stems of Lycopodium and in the 
margins of the vascular bundles of Juniperus leaves, de Bary stated that 
they are somewhat flattened, cylindrical rods branching irregularly on all 
sides, the branches fusing with one another to form a network through the 
cavity in some cases, and in others forming thickenings on the walls of the 
tracheides. In the leaves of Juniperus their points of attachment and 
origin are especially the margins of the bordered pits, in Lycopodmm the 
margins of the spiral or reticulate thickenings of the lateral walls. In 
Biota orient alis in the vascular bundles of the leaves the swollen margins 
of the bordered pits are often elongated into blunt cones, which protrude 
into the cavity, but end blindly without coalescing with one another or with 
the opposite wall. With these facts before us, the projections found on the 
inner walls of the ray tracheides of Pinus might also be compared with 
Sanio’s bars, for they project into the lumen of the tracheides, as do the 
ingrowths in the leaves of Juniperus. 
In 1890 C. Muller (6) pointed out the wide distribution of these bars, 
and he gave them the name of £ Sanio’s bars ’, indicating that they occur in 
the four groups of Coniferae (Abietineae, Cupressineae, Podocarpeae, and 
Taxineae). Muller further indicated their possible mode of development, 
and discusses three possible modes of origin as follows : 
1. The bars are secretion products of special protoplasmic accumulations 
in the cambium cells. 
2. The bars are produced by partial reabsorption of the transverse 
walls of tracheides. 
3. The bars are formed by an infolding of the tangential walls of the 
tracheides. 
In support of (1) he compared the formation of a cell-wall in cell- 
division where the new wall is formed from the protoplasm, the formation 
of a cell- wall in a V aucheria filament when injured in any way, and the 
formation of cell pegs or bars in Caiderpa. His objection to (1) is that if 
the bars are produced in this way it is not easy to see why they should not 
