6og 
Sieve-Tubes of Pi] ms. 
side of the lamella ( m.l .) are seen callus-rods and slime-strings, but on the albu- 
minous cell-side ( alb.c .) groups of protoplasmic connecting-threads (c.t.) occur. 
Fig. 13. An empty sieve-plate, showing open pores. 
PLATES XXXII AND XXXIII ( Original Figures ). 
The lenses used were Swift’s and ^ apoc. with b. and c., and 6, 8, and 
1 2 compensating oculars. 
PLATE XXXII. 
Finus excel 'sa. 
Fig. r. A microphotograph of a transverse section through the phloem (/.), 
cambium (c.), and xylem (x.) of a piece of material of Finus excelsa cut from the 
main trunk. The gradual passage from the cambium to the xylem is seen, and on 
the phloem side the sharp line caused by the boundary layer of sieve-tubes ( b.c .) is 
clearly marked. The sieve-plates ( sp .) can be seen as small dark patches on the 
radial walls of the sieve- tubes (si.). 
The cells with dark contents are either bast-parenchyma cells or sieve-tubes 
filled with resin. 
The medullary rays (mr.) are also clearly shown. The youngest sieve-plates in 
which threads have been seen occur just on the cambium side of the boundary 
layer. 
Fig. 2. A small piece of the phloem-tissues in transverse section stained with 
Congo red. The cellulose portion of the wall is stained deep pink, whilst the 
pecto-cellulose lamella and medullary ray cell-wall, &c. only stain pale pink. 
Fig. 3. A similar section to Fig. 2 stained with watery methylene blue ; the 
younger cellulose layers are scarcely stained, the middle lamella is deep blue and 
the medullary-ray walls, which are less pectic than the lamella, a pale violet-blue. 
These two figures should be compared with the diagrammatic figure (Fig. 11, 
PI. XXXI). 
Fig. 4. A sieve-plate in transverse section, showing slime-strings with median 
nodes, and a slight indication of callus-rods— prepared from fresh material by 
Russow’s method — the sulphuric acid (eighty-one per cent.) only used momentarily. 
( x 75°0 
Fig. 5. A section of a sieve-plate as above, after longer treatment with sulphuric 
acid. ( x 1000.) 
Fig. 6. A fresh section examined in Russow’s callus reagent ; slime-strings and 
median nodules are seen, but the callus-rods were not well defined. ( x 500.) 
Fig. 7. A young sieve-plate in transverse section stained with water-blue ; 
the callus ( k .) is seen growing towards the middle lamella in finger-like processes, 
and between these rods protoplasmic threads with median nodes are dimly seen. 
( x 1000.) 
Fig. 8. Transverse section across the sieve-tubes of the boundary region, showing 
three sieve-plates, the youngest (a) shows fine protoplasmic threads in groups, each 
thread with a median dot ; the one in the middle ( b ) is somewhat thicker, also 
with protoplasmic threads ; whilst the oldest (c) shows slime-strings with a darkly 
stained, median granule (stained by acid-violet method), (x 750.) 
Fig. 9. Transverse section of young sieve-tubes, showing sieve-plates in the 
transitional stage ; the youngest (a) is as yet unacted on by ferments, but in both 
