Vol. V1., No. 40.) BULLETIN oF THE Torrey BOTANICAL Cius. [New York, April, 1878. 
§ 226. A Nostoc the Matrix of Scytonema.—Among the fresh 
water Alge there is a genus Nostoc, embracing about seventy species 
described by European and American authors. A Nostoc is a 
gelatinous sack (thallus), more or less firm, usually sub-globose, 
filled with watery endochrome in which are’ embedded moniliform 
filaments. Nostocs vary in size; some-do not exceed the diameter 
of a human hair, others are of the size and form of peas and cherries; 
some are indefinitely expanded. They are found on dripping rocks, 
in pools and springs, on the ground, on trunks of trees, old wood, 
etc. The Nostoc has generally been considered a perfect plant. 
Dr. Itzigsohn, Professor J. Sachs and J. Baranetzky, however, have 
looked upon it as of doubtful character, and thought they traced a 
relation between one form, Nostoc commune, and the lichen genus 
Collema. Other authors, however, do not consider their position 
tenable. 
A careful study of a number of forms has led me to the con- 
viction that Nostocs are not perfected plants, and, reasoning from 
analogy, I would call them the matrices of Scytonema. I believe the 
many forms of the large genus Scytonema are all evolved from them. 
For illustration of the general principle I take several forms. 
The one that first elicited my attention was collected in Florida, by 
H. W. Ravenel, from the bark of a Cypress tree. The plant evolved 
from it, Scytonema mirabile, n. sp. is very distinct in the so called 
twinned pseudo-branches, and, hence, particularly suited for tracing 
the various stages of development, 
Having reference to the plate, figs. A, A, represent two small 
matrices (nostocs) in their normal character. B, another form, in 
which the filaments, which possess an Oscillaria-like power of move- 
ment, have arranged themselves in sub-parallel order. C, an older 
form, partially faded, and apparently diffluent. Many do really 
die and pass off in this manner, but here and there one comes to 
maturity and evidences by faint outlines the developing forms of 
the true plant. These are vermiform figures nestled together in the 
matrix, (C). When at full maturity for delivery, the matrix breaks 
and the young plants escape ; these are usually more or less fusi-form 
(E, E,) thin, membranous, with but a slight indication of an internal 
filament. These forms are often so distinct from the matured plant, 
a, 
that they could not be identified except by tracing them from their - 
origin to their full development. In the process of growth the young 
plants present many forms; F, the first stage of a twinned branch. 
G, H, J, J, are apparently more advanced growths. ‘l’hese 
may be faded forms of young plants, nevertheless they represent 
different stages of development. Fig. R isa perfected plant. The 
specific features are the frequent twinned pseudo-branches adhering, 
and usually without separation of the trichoma, at the end. 
For my second illustration I take forms collected repeatedly 
during the past summer in this vicinity from dripping rocks; they 
are Nostoc sphaeroides, Ktz. and Nostoc riparium, Céssati. Among 
the larger forms in older condition, some are found in which the 
young, immatured filaments may be distinctly seen. 
l= 220° | 
