186 SECTIONAL ADDRESSES. 
discussing the relation of Chorda to the Laminariacee. Killian (1911), 
describing the development of the tissues in young plants of Laminaria, 
seems to hold the view that the thickenings are artifacts. 
In a forthcoming paper an account will be given of some work of my own 
on these structures. Only the more important conclusions will be mentioned 
here. There can be no doubt whatever that the thickenings are normal 
structures, as they can be seen equally well in sections of fresh material 
mounted in sea-water, and in well-fixed material. In optical section, 
the outer limit of the wall of the hypha is perfectly even, while the inner 
is sharply ridged or serrated. In surface view, parallel lines or nearly 
parallel lines are seen running from the serrations across the tube. These 
suggested to Rosenthal the idea of spiral markings ; really, however, they 
are reticulate. In badly-fixed material there may be crumplings of the 
walls, due to a longitudinal contraction of the medulla, or delicate trans- 
verse or oblique striations, which are, however, outside the walls, and are 
due to the contraction of the outer mucilaginous layer being less than 
that of the inner wall. In most cases the bulbous dilations on either side 
of the sieveplates are unequal in size; and where this is the case they 
have a definite orientation, the bigger bulb being on the upper (distal) 
side. It is interesting to note that the reticulate thickenings are not — 
continued into the larger bulbous expansion. It frequently happens, as in 
the higher plants, that fixed material shows the presence of much coagulated 
substance, which in most cases is located in the upper part of the segments, 
against the lower surface of the sieve-plates. It had already been found by 
several investigators that the substance of the cross-plates is very different 
from that of the wall. The application by the writer of the same and other — 
tests shows clearly that the thickening layer is also different from the rest 
of the wall, and that its reactions resemble in many respects those of the 
very resistant cross-walls. The true trumpet-hyphe pursue a vertical — 
course among the web of ordinary hyphe, many of which show 
similar ‘ trumpet’ ends, which, as Church points out, ‘are not so much ~ 
dilated, as expressing the full-sized transverse septum of the elongated — 
units.” There can be no doubt that many writers have confused the two — 
kinds and thus arrived at wrong conclusions; but the presence of the © 
thickenings will always enable us to distinguish the true trumpet-hyphe — 
from the others. They occur in all typical Laminariacee. Oliver gives — 
a list of eight genera in which they are found ; to these I have been able to — 
add five. They occur even in the insignificant Adenocystis. Theone striking — 
exception is Saccorhiza. This and other considerations raise the question — 
whether this curious plant should be included among the Laminariacee. — 
Oliver points out that in Macrocystis the trumpet-hyphe never show — 
connections with the true sieve-tubes. Several writers, relying on sections 
of alcohol material, where the tissues are compressed and distorted, have — 
complained of the difficulty of tracing the courses of the trumpet-hyphe. — 
It is not difficult, however, to tease out the tubes. Thus, from the inner | 
surface of a hollow stem of Macrocystis, the writer obtained masses of 
woolly threads; consisting entirely of beautifully regular trumpet-hyphe. 
The facts suggest several interesting problems :— 
1. What is the function of the tissue? Is it storage, conduction — 
of food material, or merely a strengthening of the whole plant ? by 
2. If it subserves either or both of the two first-named functions, how | 
