462 DR. P. GROOM AND MR. W. RUSHTON ON THE STRUCTURE 
are farther apart, they are separated by a streteh of wall that gives the full 
reactions of lignified membranes, and Sanio’s rims are bands confined to 
the neighbourhood of the pits. In Pinus excelsa there is additional evidence 
that the structure at least of the inner layer of the radial wall centres round 
the pit-areas bounded by Sanio’s rims: for when two uniseriate pits are at 
some distance apart the space intervening between them is occupied by the two 
narrow fringing curved bands (Sanio’s rims), and between these by a stretch 
of wall showing striations which near the bands are curved in the same sense 
as these, but at increasing distances from the bands show decreasing curva- 
ture until midway between the two pits the striæ are straight and transverse. 
All the Indian species of Pinus show Sanio’s rims. In P. eacelsa and 
Р. Gerardiana in the primary pit-area only one pit forms but occasionally 
two side by side may arise, whereas in the other three Indian species two 
pits are commonly produced side by side in one area. But P. Merkusii is 
unique among known living pines in that in one primary pit-area there may 
be produced either three pits side by side, or three forming a cluster, of 
which two are lateral and approximately side by side, while the third is 
median above or below, or finally four forming a cluster like the last except 
that there are two median, one above and one below (Pl. 25. figs. 43, 47, 48). 
Other deviations regarding the arrangements are deseribed in the detailed 
description of P. Merkusii, Sometimes Sanio’s rims completely surround 
, 
become a single fringe or margin (figs. 43, 46, 47). 
the pit-bearing area, that is, also on the sides ; in such a case they literally 
The detailed structural relations in regard to these Sanio’s rims we 
investigated in connexion with P. Merkusti. In radial sections with iodine 
and sulphuric acid the “rims” stain yellow : with ordinary hematoxylin 
they remain unstained ; leaving sections in cupra-ammonium to dissolve out 
any cellulose, their staining properties are not changed materially. They 
are not composed of cellulose. They stain more deeply than the rest of the 
wall with iron-hematoxylin, with methylene-blue followed by immersion in 
2 per cent. acetic acid, also with ruthenium-red. Treating radial sections 
with ammonium oxalate, or successively with 2 per cent. hydrochloric acid 
for half an hour and then boiling for two hours in 2 per cent. caustic soda, 
they do not stain with ruthenium-red or with methylene-blue and acetic acid. 
Therefore ** Sanio's rims ” are at least partly pectic. 
Now the fact that a single straight band may be seen in radial section 
continuing aeross two or more tracheids, proves that the phenomenon is 
associated in some manner with the middle lamella. In tangential sections 
the appearance of these bands is seen to be due to a circular, or. fusiform 
band-like, localized thickening of the middle lamella : where two successive 
superposed pits are close together the thiekening between them is single, but 
where the pits are some distance apart there are two such thickenings, one 
