The Histology of the Sieve-Tubes of Pinus. 
ARTHUR W. HILL, M.A., 
Felloio of King's College , Cambridge , and Demonstrator of Botany in the 
University. 
With Plates XXXI, XXXII, and XXXIII. 
HE sieve-tubes of the Coniferae have been previously 
X examined and described by several botanists ; but the 
conclusions at which they have arrived do not always agree 
together, and a good deal of uncertainty exists in consequence 
on questions concerning the development and the character of 
the means of communication between adjoining sieve-tubes. 
It therefore seemed advisable to carefully reinvestigate the 
sieve-tubes of Pinus by means of the methods elaborated by 
Walter Gardiner 1 , which have also recently been used to 
demonstrate the presence of f connecting threads ’ throughout 
the tissues of some species of Pinus 2 . 
Before the present results are described, some notice must 
be taken of the work already published on this subject. 
1 W. Gardiner, Roy. Soc. Proc., vol. lxii, 1897. Camb. Phil. Soc. Proc., 
vol. ix, pt. viii. 
2 A. W. Hill, ‘ The Distribution and Character of “Connecting Threads” in 
the Tissues of Pinus sylvestris and other allied Species * (Part I of Gardiner and 
Hill on ‘The Histology of the Cell- wall’). Phil. Trans. Roy. Soc. B., 
vol. cxciv, 1901, pp. 83-125. 
[Annals of Botany, Vol. XV. No. LX. December, 1901.3 
