Spore Formation in Botrychium virginianum. 
BY 
WILLIAM C. STEVENS, M.S., 
Professor of Botany , University of Kansas, U.S.A. 
With Plates XXVIII, XXIX, and XXX. 
I N Botrychium virginianum the development of the sporangia begins 
a year previous to their ripening. Plants which are dug up about 
the time of the shedding of the spores show next year’s leaf with sporangia 
just forming, enclosed by the stipule-like sheath at the base of the leaf 
of the present year. The youngest sporangia are then in the form of slight 
elevations. At the apex of each of these is a pyramidal cell which divides 
by a periclinal wall, and the inner of the two cells thus formed is the 
archesporium which, by repeated divisions, gives rise to the spore-mother- 
cells (Campbell, ’95). 
As soon as the leaves come above the ground in the spring the spore- 
mother-cells are found in the condition represented in Fig. i, evidently 
in the early prophase of their first division. The spore-mother-cells are 
then seen to be demarked from each other and from the tapetum by a deli- 
cate plasmatic membrane. They are not, as a rule, united into a single 
mass, but are separated into groups of four to thirty-five. It is possible, 
however, that the separation into groups in this early stage is done in the 
preparation of the sections, but, at any rate, we may be sure that the 
tendency to separate exists, since in later stages we find like groups immersed 
in the plasmodium of the tapetal cells that has flowed in between them. 
At this stage the nuclear thread is rather loosely-coiled (PL XXVIII, Fig. i), 
its windings, where applied to the nuclear wall, showing some degree of 
symmetry (Fig. 3 ). With the safranin-gentian violet-orange method the 
nuclear thread is at this stage stained a uniform purple or violet, showing 
no differentiation into chromatin and linin disks. Usually but one nucleolus 
is present, but as many as two or three are sometimes found. 
The tapetum in this early prophase consists of two layers of cells 
of varying form and size, each cell being deliminated by a plasmatic 
membrane merely, which, in some instances, is incomplete, so that there 
is a fusion of the cytoplasm of adjacent cells. This fusion is progressive 
[Annals of Botany, Vol. XIX. No. LXXVI. October, 1905.] 
K k % 
