6 04 HilL — The Histology of the 
experiments to be performed, and Pfeffer 1 doubts whether 
the threads are of any use for the purpose. Brown and 
Escombe 2 , however, have recently attacked the problem from 
the physical side, and have come to the conclusion that, given 
certain conditions, ‘ the flow of the diffusing substance may 
go on almost as rapidly through a ‘‘multi-perforate septum” 
— such as that provided by a pit-closing membrane studded 
with threads — as if no closing membrane were present.’ 
Therefore — -and these remarks apply with equal weight to 
the slime-strings of the sieve-plate— it seems highly probable 
from the study of the general distribution of connecting 
threads throughout the tissues and from a consideration of 
their enormous numbers, that their cumulative effect must be 
of great importance in translocation. 
The slime-strings of the sieve-tubes of Angiosperms, owing 
chiefly to their size and position, have always been regarded 
as important factors in the translocation of the elaborated 
food materials, and there is no doubt but that the smaller ones 
in the sieve-plates of Pinus perform similar functions to those 
of other plants. 
The present research, however, has yielded results which 
seem to prove that a passage of substances in solution can 
and does take place by means of the protoplasmic thread 3 . 
The mere fact that the thread of the developing sieve-plate 
becomes converted into the slime-string of the mature sieve, 
1 Pfeffer, ‘ Physiology of Plants ’ (Eng. ed.), 1899, p. 112, sect. 20. He gives an 
erroneous figure of ‘ connecting threads,’ and there is no reference to any of 
Gardiner’s work, an omission which should have been rectified by the editors 
of the English translation. The text is therefore largely based on the incorrect 
results of Kienitz-Gerloff’s papers. 
2 Brown and Escombe, Phil. Trans. Roy. Soc. B., vol. cxciii, 1900, pp. 280, 
281. Measurements of ‘connecting threads ’ have been given in the paper on 
Pinus, Gardiner and Hill, pt. i, Phil. Trans. Roy. Soc. B., vol. cxciv, 
pp. 87, 88. The approximate dimensions of the individual threads appear to be in 
length 1*8 ju, and .3 /* in diameter. In the thin tangential wall of the medullary ray 
cells, in the cambium of P. excelsa , each thread was not more than 1 *6 >u. long, and 
in such a wall they appeared to be so arranged that about nine threads occurred in 
every 4 sq. n of area. 
3 Cf. the action of the ferment on the cell-walls and threads of Tamus endo- 
sperm. 
