464 DR, P. GROOM AND MR. W, RUSHTON ON THE STRUCTURE 
close to the pit ; it only broadens very slightly where it is forking just before 
passing into the wall of the pit-chamber ; moreover, the staining of the 
middle lamella with ruthenium-red is the same throughout and is rather 
light. 
It is worthy of note that in staining radial sections with ruthenium-red or 
with methylene-blue, the part of Sanio’s rim that stains most readily and 
deeply is frequently the part immediately beneath the eentre of the pit, and 
when the Sanio's rims are dwindling in the outer spring-wood or inner 
summer-wood it is lateral or marginal parts that vanish first while the 
central parts remain. 
As there appears to be some confusion concerning the meaning of the term 
“Sanio’s bars" some comments may be made, In radial longitudinal 
sections of coniferous woods the appearance of transverse bands running 
across the tracheids is caused by three entirely different sets of structures :— 
(1.) There are bars or rods stretching across the lumen from tracheid to 
tracheid and forming a continuous radial series, extending through a few 
tracheids or through one or more annual rings. Similar bars often extend 
across the lumina of sieve-tubes. In the wood these are lignified, but in 
the phloem they react as cellulose. C., Müller (1890) was the author of the 
name * Sanio's bars" and, as he explicitly stated, he coined the term to 
designate these structures as first discovered by Sanio in Pinus sylvestris 
(1873-4). In a radial section the individual rods are seen to form a 
continuous line and only one such series is seen, as a rule, in a single 
longitudinal radial section ; these rods then are limited in number. 
C. Müller (1890), on the basis of his observations, formulated the proposition 
that Sanio’s bars occur in all the sub-groups of the Conifer (including 
Araucaria and Ginkgo) and that they arise as folds of the radial walls. The 
proposition as to Sanio’s bars has been incorrectly restated by Miss Gerry *. 
(i1.) There are structures known as * resin-plates ” arranged somewhat in 
the same manner as seen in radial section. They are found most frequently 
or exclusively in contact with medullary rays. In radial section they are 
‘generally deeper than Sanio’s bars, usually clearly dilated against the tracheid 
wall, and often form a complete partition dividing the lumen of the tracheid 
into two chambers. 
Gii.) There are certain markings which form a pattern on the radial walls 
ef the tracheids, especially in the spring-wood, The markings are largely in 
the form of transverse bands, but contrast with the other bands seen in 
radial section in that in every spring-tracheid numerous bands are visible, 
* Gerry, in Ann, Bot. xxiv. (1910) pp. 119-128, 
