ON THE PILOBOLIDiE 
259 
with these zygotes, which both the before-mentioned observers 
considered to be very rare, each having met with them on 
only one occasion. 
The spores, which Van Tieghem sowed in a pendent drop 
of nutrient liquid,* in a closed cell, germinated and produced 
a shortly ramified mycelium. Two days after conjugations 
were observed between neighbouring branches ; two short 
lateral ramuli (which even in some cases proceeded from the 
same branch of the mycelium), growing in a flexuose manner, 
twined round each other a few times, and their free ends, 
swelling somewhat and curving towards one another, came 
into contact. The terminal portion of each was then 
separated from the rest by a septum, the two cells thus 
formed being constantly unequal. These became more and 
more closely united with each other, the intervening mem¬ 
brane disappeared, and their protoplasmic contents were 
mingled. The zygote thus formed surrounded itself with a 
thickened membrane, which became black and smooth; they 
reached a size of about 40 /*, but did not develop further. 
Brefeld found his zygotes already fully developed on 
horse-dung, on which the fungus was growing luxuriantly. 
They were black, of an oval form, 100 by 120^, and covered 
with little warts; when ruptured they were seen to enclose, 
within the blackened exospore, a thick-walled, smooth endo- 
spore, and within that a dense protoplasm. After lying for 
four weeks on damp paper they germinated, giving out a 
tube which immediately produced the ordinary sporange of a 
Pilaira. 
PART III.—CHEMICAL REACTIONS. 
Of these, to which I have paid little attention, I will 
only mention a few. A solution of iodine in potassic iodide 
imparts to the stem of Pilobolus a beautiful rosy tint, 
passing into reddish purple with a stronger solution, 
a reaction which is very characteristic of the Mucorini. 
Iodine colours the spores at first green, then brown. Thus 
if a spore-mass, unbroken, be treated with iodine solution, 
the reagent penetrating gradually inwards, but not reaching 
the centre, where the orange spores still remain in their 
normal tint, produces concentric shells of colour which have 
a very pretty effect. Strong sulphuric acid removes the dark 
(sometimes brown, sometimes violet-black) pigment from the 
cuticularised membrane of the sporangium, causing it to 
* 
The liquid used was a decoction of dung. 
