the Sieve-tubes in Laminarieae. 
97 
tissue which is especially interesting to us. This consists of a 
meshwork of hyphae running in various directions and em- 
bedded in a mucilage formed by the breaking down of the 
outer layers of their walls. Amongst these hyphae a careful 
examination of a longitudinal section will show a number of 
narrow tubes running longitudinally, their walls (in alcohol- 
material examined in glycerin) showing a marked striation as 
well as stratification. These are devoid of septa except at 
certain points where the hypha is swollen up spherically. 
The septum runs horizontally across this enlarged portion, 
and is considered to represent a sieve-plate, as a protoplasmic 
continuity is demonstrable through it. These tubes have 
received the name of sieve-hyphae (Siebhyphen) or trumpet- 
shaped hyphae (Trompetenformige Hyphen); I shall here 
refer to them, for brevity, always as trumpet-hyphae. Wille 1 
was the first to carefully figure them, though Reinke 2 had 
previously described them ; they are occasionally roughly 
suggested in the anatomical sketches of the older phyco- 
logists 3 , who however simply refer to them as ‘ hyphae swollen 
at the joints.’ 
These trumpet-hyphae occur universally amongst Lamina- 
rieae in the medulla ; I have noticed them in Laminaria , 
Alaria , Agarum y Thallassiophyllum , Ecklonia y Lessonia , 
Macrocystis and Nereocystis. Grabendorfer 4 figures them for 
Lessonia ovata . To the trumpet-hyphae I shall refer in 
detail later on. 
No other form of sieve- tube is found in Laminaria , or 
indeed in the majority of the above quoted genera of 
Laminarieae , but in Macrocystis and in Nereocystis there is, 
around the central strand of hyphae, a zone of tubes with 
3 N. Wille, Siebhyphen bei den Algen, in Ber. d. deutsch. bot. Ges. 1885, 
p. 29 ; also, Bidrag til Algernes Physiologiske Anatomi, Kongl. Svenska Vetens. 
Akad. Handl. B. xxi. No. 12, Stockholm, 1885. 
2 J. Reinke, Beitrage zur Kenntniss d. Tange, in Pringsh. Jahrb. f. w. Bot., Bd. x, 
P-317- 
3 Kiitzing, Phycologia Generalis, Tab. 32 j Postels and Ruprecht, Illustrationes 
Algarum, 1840. 
4 J. Grabendorfer, Beitrage z. Kenntniss d. Tange, in Bot. Ztg. 1885. 
