292 Sykes. — Anatomy and Histology of Macrocystis pyrifera and 
figures both in Macrocystis and in Nereocystis . His description was followed 
by a paper from Rosenthal 1 , who disagreed with him on many points con- 
cerning the anatomy and histology of Macrocystis . Three years earlier 
had appeared Oliver’s 2 results, on the subject of the obliteration of the 
sieve-tubes in Macrocystis and Nereocystis. 
In 1897 Macmillan 3 described the external features of Nereocystis , 
paying, however, only very small attention to the anatomy. Finally Wille 4 5 , 
in 1897, again investigated the trumpet hyphae in Alaria and other Lami- 
nariaceae, and made an attempt to group the tissues in this family into 
various physiological systems. 
Will 6 and Rosenthal 6 both studied the development of the young 
tissues in Macrocystis , and Setchell 7 , during the course of his description of 
Sacchoriza dermatodea , gives a short and useful account of the youngest 
stages in that plant. A short summary of most of the above papers is 
given by Oltmanns 8 . The conclusions arrived at by these various authors 
are sometimes at variance, but the following is an attempt to sketch some 
of their principal points. 
i. Development in young plants. The general ground-plan of structure in 
all Laminariaceae is the same. The tissues of the adult may be broadly 
differentiated into 'cortex’ and ‘central body’ ; though no sharp line can 
be drawn between these two regions, since it is found that in the course of 
development the inner layers of the cortex give rise to the outer layers 
of the central body. According to Setchell 7 the development of the 
central body in Sacchoriza takes place in the following manner. In the 
very young plant the innermost cells of the thallus soon cease to divide, 
and thus form the first constituent of the medulla, becoming much 
stretched owing to the great growth in length of the surrounding tissues. 
Later the adjoining layers of cells add to the medulla, and are, in a similar 
manner, stretched and elongated. The longitudinal walls of all the cells 
forming the central body become greatly swollen by the conversion of the 
middle lamella into slime, giving rise to the appearance of a number of 
isolated rows of filaments. These rows are connected by short cross 
connexions, which later become stretched by the swelling of the walls ; 
they are considered by Setchell to be formed from the pit canals between 
the original central cells. In addition to these a large number of hyphae 
1 Rosenthal, Zur Kenntnis von Macrocystis und Thalassiophyllum. Flora, 1890, p. 105. 
2 Oliver, On the obliteration of the sieve-tubes in the Laminariaceae. Annals of Botany, i, 
1887, p. 95. 
3 Macmillan, Observations on Nereocystis. Mem. Torrey Bot. Club, 1897, p. 273. 
4 Wille, Festskrift til H. Maj. Kong. Oskar II, 1897, Regieringsjubilant. 
5 Will, 1 . c., 1884. 6 Rosenthal, 1 . c., 1890. 
7 Setchell, W. A., Concerning the life-history of Sacchoriza dermatodea. Proc. Amer. Acad., 
1891, 26, p. 177 (Crypt. Lab. of Harvard Univ., 17). 
8 Oltmanns, Morpbologie und Biologie der Algen, vol. i, pp. 445-458. 
