422 
Rushton . — The Development of 
confusion arising therefrom it appeared desirable to reinvestigate their 
development. Specimens from about twenty-five species of Pinus were 
obtained in May, 1914, and fixed in watery picric acid. 
Amongst the species collected was Pinus Inops , which, on examina- 
tion, showed the bars most frequent, and so appeared most suitable for 
investigation. 
Transverse, radial, and tangential sections were taken ; for transverse 
and radial hand sections were found most suitable, but for tangential the 
X C p k . 
Fig. 1. Transverse section of Pinus Inops , showing ‘ Sanio’s bars’ crossing xylem (a:), cambium (V), 
and phloem (pk). x 520. 
microtome was used after embedding the wood in paraffin wax of 52 0 C. 
melting-point. 
In transverse sections the bars were found to cross the lumina of the 
tracheides as relatively thick lignified rods, and in the cambium to be merely 
fine thread-like structures with cellulose walls, these threads sometimes 
widening out again in the bast or retaining their thread-like character, but 
still with cellulose walls. The way in which the bars cross the cambium 
and phloem could be more easily seen in radial than transverse sections, 
where, in addition to crossing the sieve tubes, the thread-like bars could be 
demonstrated crossing the phloem parenchyma (Figs, i and 2). 
Fig. 2. Radial section of Pinus Inops , showing bar of Sanio crossing xylem (x), cambium (<:), 
and phloem (pk). X 415. 
The most interesting part of the investigation came out in the serial 
microtome-cut tangential sections, where whole series of sections could be 
obtained, tracing the bar outwards from the xylem through the cambium 
and into the phloem, the bar appearing in section throughout. 
In the xylem region the bar appears as a hollow tube varying in out- 
