Laminaria saccharina. 
297 
Callus and slime-string formation are also described by Will \ Wille 2 , 
and Rosenthal 3 in Macrocystis , and by Wille 2 in Alaria , and the sug- 
gestion is several times advanced that the development of the sieve-plate 
will be found, on further investigation, to be similar to that in Angiosperms. 
Since all these authors worked on dried or alcoholic material, the finer 
histological details of the protoplasmic threads and of callus-formation 
could not be studied. 
iii. Protoplasmic continuity. Hick 4 in 1885 attempted by various 
and somewhat drastic methods to demonstrate protoplasmic continuity in 
Ascophyllum and Fucits. The chief interest of his experiments lies in the 
demonstration which they afford of the great resistance of these algal cell- 
walls to powerful chemical reagents. 
Rosenthal’s attempts to demonstrate continuity of protoplasm appear 
to have been more successful. He does not figure his results, but describes 
slime-strings in the sieve-tubes and connexions through the pit-closing 
membranes of the cortical cells. 
Oliver also describes protoplasmic continuity in the young trumpet 
hyphae and sieve-tubes of Macrocystis. 
(c) The objects of the present research. 
From the foregoing review it will be seen that several points require 
investigation. 
I. Anatomical. 
i. The morphological nature of the ‘ trumpet hyphae ’ and so-called 
f true sieve-tubes ’ in Macrocystis and Laminaria. 
ii. The nature of the growth in thickness of the medulla in Macro- 
cystis. 
iii. The formation of secondary connexions by the hyphae growing 
into the medulla in both plants. 
II. Histological. 
i. The question of the presence or absence of protoplasmic connecting- 
threads across the cell-wall. 
ii. The development of the sieve-plate in Macrocystis and Nereocystis, 
and of the cross walls of the trumpet hyphae in these and other species, and 
its comparison with the development of the Angiospermous sieve-plate 6 . 
iii. The nature of the callus found obliterating the older sieve-plates 
and formed throughout the length of the trumpet hyphae and old sieve-tubes. 
The question whether it is a cell-wall production, due to alteration of already 
formed cellulose, as described by Oliver, or whether it is deposited by the 
1 Will, 1 . c., 1884. 2 Wille, 1 . c., 1885. 3 Rosenthal, 1 . c., 1890. 
4 Hick, Protoplasmic Continuity in the Fucaceae. Journal of Botany, xxiii, 1885. 
5 Hill, A. W., Histology of the sieve-tubes in Finns. Ann. of Bot., xv, 1901. Historical 
Summary, pp. 576-585. 
X 
