218 «+ 
Kiitzing, Agardh, Cessati and others describe Nostocs which have 
the filaments sometimes sheathed, not always, and usually indistinctly, 
“indistinctis vel diffluentibus.” The descriptions given accord well 
with the appearances of these forms,(M). The process of develop- 
ment in some is not unlike the one before described. In others it is 
quite distinct. I had several matrices, which after having been kept in 
water eight or ten days, literally fell to pieces under slight pressure, 
and spread out a whole nest of young Scytonema filaments (W; W) 
linear, short, somewhat curved and membranous forms. These 
elongate into filaments, (V, V). 
In other Matrices (N) the sheathed filaments break up into 
smaller parts, each of which forms a separate cell or sack, in which the 
cellules of the parts of the moniliform filaments divide and multiply. 
After a time the distended epidermis of the matrix breaks, and the 
young are scattered. These are usually subspherical (P) or oblong 
(Q) and often in series, two to six united, (P, Q). Each contains a 
single filament, more or less coiled A heterocyst generally makes 
a link of union. In the process of development the filament uncoils 
and lengthens, the epidermis at first subspherical (P) elongates also 
(Q) and finally when the filament is straightened out (S, T) the 
epidermis is brought close to it, and thus constitutes the sheath of 
the trichoma, (T). 
The young plants vary in size, and undeveloped they may easily 
be mistaken for distinct species. X, X are fully matured plants. 
Very young forms (Q, T) are occasionally observed to put forth the 
characteristic double pseudo-branches. 
Nostocs of other forms, and particularly those of irregularly ex- 
panded thalli, develop the plants by a more simple process. The 
cellules of the moniliform filaments expand and unite; the walls of 
union are absorbed and thus a continuous filament is formed, which 
develops the true plant. Specimens of this kind occur among 
gatherings made at Niagara, and in this vicinity, but the most per- 
fect were found among the extensive collections made by C. F. 
Austin and J. Donnell Smith during the past month of March in 
South Western Florida. In a small portion of the gelatinous mass 
of a matrix, no larger than to be visible under one-fifth objective, the 
various stages of development may be seen intermingled. 
There is a form of a plant which I often found difficult | to 
' separate from the true Scytonema because it is so much like it, but 
sometimes in part, assumes the Tolypothrix character. The life 
history is distinct and separates it readily. 
Matrices appear to be of three kinds. The majority are sterile, 
others develop Scytonema, and a third class, apparently reproduces 
its like in the manner hitherto described by many authors. 
Many details and peculiarities might be added, but the object of 
this article is not to present a full history, but simply to record facts 
for the benefit of those interested in this subject, and to aid in farther 
examinations. One thing more may be noticed, the circumstance that 
led to these investigations, that is, that Nostocs and Scytonema are usu- 
ally found together, more or less intermingled, sometimes the one and 
sometimes the other predominating. FRANCIS WOLLE. 
