On the Obliteration of the Sieve-tubes in 
Laminarieae. 
BY 
F. W. OLIVER, B.A., B.Sg., F.L.S. 
With Plates VIII and IX. 
HE nature of the bodies which are found in sieve-tubes 
JL blocking up the perforations has in recent years formed 
the basis of a great deal of discussion. These were originally 
discovered, it will be remembered, by Hanstein 1 , and to them 
he gave the name of callus. Since their discovery our know- 
ledge of sieve-tubes has progressed rapidly, due chiefly to the 
researches of Russow 2 , Wilhelm 3 , Janczewski 4 , Strasburger 5 , 
Fisher 6 , and Gardiner 7 . 
Callus-plates are found universally amongst Phanerogams, 
but in vascular Cryptogams they are known only for a limited 
number of cases 8 . In the lower groups 9 of Cryptogams they 
are entirely unknown, indeed we have only just begun to 
1 Hanstein, Die Milchsaftgefasse. Berlin, 1864. 
2 Russow in Sitzb. d. Dorpater Nat. Ges. 1881, pp. 63-80, 1882, pp. 350-389. 
3 K. Wilhelm, Beit^ge zur Kenntniss d. Siebrohrenapparates. Leipzig, 1880. 
4 Janczewski, Etudes comparees sur les tubes cribleux, in Mem. de la Soc. 
d, sc. nat. de Cherbourg, XXIII (1880), p. 300. 
5 Strasburger, Bot. Pract. I. Aufl. p. 1 50. 
6 A. Fischer, Ueb. d. Inhalt d. Siebrohren in d. unverletzten Pflanze, in Ber. d. 
dent. bot. Ges. 1885 ; also, Neue Beitrage z. Kenntniss d. Siebrohren, in Berl. Ges. 
Wiss. 1886, p. 291. 
7 W. Gardiner, Obs. on the constitution of Callus, in Proc. Cam. Phil. Soc., 
vol. v (1885), p. 230. 
8 i. e. Alsophila australis, Balantium antarcticum , Osmunda regalis . Equi' 
setum arvense, according to Russow. 
9 The ‘ stoppers’ found in connection, with the perforations in many red- 
seaweeds require further investigation. Cf. Archer on Ballia callitricha , in 
Trans. Linn. Soc., New Series, Bot. vol. i. 
[ Annals of Botany, Vol. I. No. II. November 1887. ] 
