The Histology of the Sieve-Tubes of Angiosperms. 
BY 
ARTHUR W. HILL, M.A. 
Assistant Director , the Royal Gardens , Kew ; late Fellow of King' s College , Cambridge. 
With Plates XVII and XVIII and thirteen Figures in the Text. 
PART I. 
Historical. 
N UMEROUS attempts have been made to arrive at a clear under- 
standing of the histological structure of the sieve-tubes of Angiosperms, 
and of their relations to the other elements of the phloem. 
Among the most important of the earlier works on this subject are the 
papers of Wilhelm, Russow, and Janczewski which appeared in the years 
1880-3. These three investigators were concerned chiefly in examining 
the structure of the mature sieve-plate and its mode of formation, although 
Wilhelm’s work in this direction occupies only a small space in his beautiful 
monograph on the phloem of Vitis. 
Fischer’s papers are the next in chronological order to which it is 
necessary to draw attention, and in them physiological rather than histo- 
logical questions are considered and very little light is thrown on the origin 
of the sieve-plate. An interesting paper, from the point of view of sieve- 
tubes in general, appeared in 1887, by Oliver, which dealt with the formation 
of the callus in algal sieve-tubes, and reference will be made to it later. 
Lecomte’s elaborate thesis appeared in 1889 and is the next important 
paper on our subject, dealing entirely with angiospermous sieve-tubes. It 
is prefaced by a well-written historical summary, so that it is unnecessary to 
give more than a short critical account of earlier work by way of introduction 
to the present research. 
Ten years later — in 1899 — Perrot published a separate treatise, entitled 
£ Le Tissu crible ’, the important part of which, from the point of view 
of this paper, is the excellent historical summary of previous research. 
Among the most recent attempts to solve the question of the structure 
and mode of origin of the angiospermous sieve-plate will be found the 
[Annals of Botany, Vol. XXII. No. LXXXVI. January, 1908.] 
