582 Hill . — The Histology of the 
tube from the next and the median nodules are also still 
visible. Thus there is no open communication between 
adjoining sieve-tubes. 
It is unfortunately by no means easy to elucidate Stras- 
burger ’s meaning by the help of his figures, for the surface- 
views do not agree with the sections, because apparently the 
callus-rods, which should correspond to the sieve-fields, are 
not indicated in the figures of the tangential sections 1 . It 
is also a difficult matter to see clearly all he describes when 
using his magnification. These results of Strasburger’s, how- 
ever, which agree so closely with those of Russow, will be 
shown later to correspond very nearly to the results obtained 
during the present research, far more. closely in fact than any 
of the subsequent views which he has published. 
The next paper bearing on the subject is that of Kienitz- 
Gerlofif 2 * to which only a passing reference need be made ; he 
gives two very indifferent figures of what must be £ slime- 
strings ’ showing median nodes, for all the callus is dissolved 
away by the strong sulphuric acid he employed in his method. 
Some new views on the structure of the sieve-plate were 
brought forward by Strasburger in his * Leitungsbahnen V 
published in 1891, which differ a good deal from those already 
noticed. 
In this work he deals more especially with the relations 
existing between sieve-tubes and albuminous cells, and this 
part has already been discussed in a former paper 4 . 
Referring to the sieve-plates 5 he agrees with Russow 6 as 
to their formation, and states that the first change on the 
surface of the membrane is a fine puncturing, which appears 
as fine points arranged in nearly circular groups, and the 
separate groups form a field of the sieve-plate. 
1 c Bot. Practicum’ ; cf. Fig. 63 with Fig. 64 A. 
2 Kienitz-Gerloff, Bot. Zeit., 1891, p. 34, and Fig. 31 A and B, Taf. i. 
:: Strasburger, * Leitungsbahnen,’ p. 60 et seq. 
4 Gardiner and Hill, ‘ Histology of Cell-wall,’ pt. I. ‘ Connecting Threads in 
Finns? by A. W. Hill. 
5 Loc. cit., p. 69 et seq. 
6 Russow, loc. cit., 1882, p. 279; also cf. bade, p. 579. 
