106 DIVISION I. GENERAL MORPHOLOGI'. 



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 spoi^ in Peziza Acetabulum, Helvella elastica, and other species. In 

 many other cases smaller drops c f oil are distribu ed 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 J . 

 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 reagent^ like alcohol, glycerine, or sulphuric 

 acid which have the power of extracting fluids ; the air-bubble disappears when 

 water repjaces these reagents. 



1 Hoffmann in Pringsheim's Jahrb. II, p. 308. 



