106 DIVISION I,—GENERAL MORPHOLOGY, 
The fatty matter which it often contains appears in many cases in the form of 
spherical drops; such a drop, often surrounded by smaller ones, occupies the 
centre of the spore in Peziza Acetabulum, Helvella elastica, and other species. In 
many other cases smaller drops «f oil are distribued without arrangement in 
the protoplasm, or are collected at fixed spots in tolerably constant numbers. The 
best known and most remarkable examples of this kind are found in the ellipsoid 
spores of Peziza vesiculosa, P. Sclerotiorum, Helvella esculenta (Fig. 58) and their 
allies, which have one or more rarely two drops of oil in their foci. In P. tuberosa and 
P. hemisphaerica on applying iodine I saw spherical or irregularly shaped bodies which 
were not previously visible make their appearance at those points, and acquire the 
reddish brown colour of glycogen while the rest of the cell-contents became yellow. 
A large proportion of the smaller granules, which are present often in consider- 
able quantities in the protoplasm, may also consist of emulsionised fatty matter '. 
The reddish yellow pigment of the spores of the Uredineae and of Pilobolus may also 
be mentioned again in this place in connection with the fatty substances. See above, 
page 7. 
If a nucleus is distinguishable in the young spores it can often be still seen in the 
same spores when they have reached maturity; but this is not always the case 
even where the protoplasm is not clouded by granules or large drops of oil. 
It has already been said that a round pellucid body is to be seen in the centre of 
the protoplasm of some acrogenously produced spores, among the Hymenomycetes, 
for instance, and in the teleutospores of the Uredineae, the real nature of which 
is still undetermined, it being uncertain whether it is to be regarded as a nucleus 
or as a vacuole. _ 
The ‘nuclei’ of older authors (before the year 1863) were for the most part 
drops of oil, the real nature of which can easily be determined by reagents. Corda 
and Tulasne, on the other hand, call the entire protoplasm of the spore the nucleus, 
which may be quite right in itself, but which is not compatible with the cell- 
terminology here set forth. 
The protoplasm of the spore in the young state is rich in water, and when dry 
absorbs water rapidly from its environment. A spore lying in water appears under 
the microscope to be filled with it to turgescence. As it loses water it contracts, and 
if the wall is thin the membrane either sinks in irregularly or forms definite folds ; 
round or ovoid spores take therefore the shape of a concavo-convex lens, the edges of 
which are often bent over towards each other, and the spore has thus the form of a 
boat. Thick-walled spores do not change their form in drying, or change it but little. 
In many cases an air-bubble is formed inside the protoplasm as it parts with water, 
as in Peziza abietina and P. melaena, in species of Sordaria, in Melanospora parasitica, 
&c.; so also in the gonidia of Cystopus (Hoffmann) and in the resting spores of Proto- 
myces macrosporus. This is due to the fact that air, that is to say, some gas, is dissolved 
in the contents of the fresh turgescent spore, and is set free as soon as the quantity of 
water is brought down to a certain limit. The same result is produced if the spore 
in the water is exposed to the influence of reagents like alcohol, glycerine, or sulphuric 
acid which have the power of extracting fluids; the air-bubble disappears when 
water replaces these reagents. 

? Hoffmann in Pringsheim’s Jahrb. II, p. 308. 
