1883. | of the Field Horsetail.. rI 
This paper contains the results of some observations upon the 
development of the male prothallium of Egutisetum arvense, made 
in the botanical laboratory of the University of Michigan, in the 
‘spring of the present year. 
Mature fertile plants were gathered on the 28th of April, and 
the following day the spores (Pl. 1, Fig. 1) were sown under glass, 
some in water and the remainder in damp earth. The second 
day after, while some were already divided into two cells, (Fig. 
3), others had just begun to throw out the root hair (Fig. 2). 
Usually the first sign of active germination was the protrusion of 
a nearly colorless tube, the root hair (Fig. 2), followed very soon 
by a division of the body of the spore into two cells by a longi- 
tudinal septum (Fig. 3 a). Sometimes the second cell seems to 
be formed by a kind of budding (Fig. 3 4), but this, though not 
uncommon, is not the ordinary method. The root-hair grows 
with extreme rapidity, especially where the spores were growing 
in water (Fig. 4), and is destitute of chlorophyll, while in the 
body of the spore the chlorophyll is abundant. Almost imme- 
diately on the germination of the spore a very perceptible change 
occurs in the chlorophyll. While in the spore before germination 
‘the chlorophyll is evenly distributed throughout, as soon as ger- 
mination begins there is a tendency in it to collect in distinct 
masses or chlorophyll bodies, which at an early stage in the 
‘development of the prothallium become very sharply marked. 
It is a difficult matter to give any definite rule for the method of 
cell division, as it differs so much in different individuals. Some- 
times, though rarely, no root-hair is given off, the spore develop- 
ing otherwise in a normal manner; again, in other cases there is 
a great enlargement of the spore without the formation of septa 
for a long time after germination commences (Fig. 8), (this was 
specially noticeable in the spores grown in water)—forming elon- 
gated flask-shaped cells. 
On May 3d the spores presented the appearance shown in Figs. 
4-6. Some were divided into four cells by longitudinal septa 
dividing the cells already formed, and in others (Fig. 5), the lower 
cell remained undivided, while the upper was divided into two, 
the cells having considerably grown in the meantime. No fur- 
ther change of importance was noted for several days, except a 
constant increase in the size of the cells. Figs. 7 æ ġc shows 
forms observed May 5th, the first showing a spore that seem 
