CHAPTER III. — SPORES OF FUNGI. — GERMINATION. 



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becomes invested with a very delicate membrane of its own and appears as a small 

 vesicle which elongates in the outward direction as the germ-tube and grows 

 through the episporium. In the thick-walled spores of Pertusaria the tubes often 

 ramify inside the episporium and the ramifications spread in it parallel with the surface 

 of the spore. The canals in the membrane are, as far as can be ascertained, new 

 formations at the time of germination, and are not enlargements of primordial forma- 

 tions. They continue usually so narrow that vesicles and germ-tubes appear at first 

 sight to be completely surrounded. On account of the slight thickness of the epi- 

 sporium in Ochrolechia these project at an early period above the surface of the spore, 

 and, as Tulasne observes, may often be separated with the episporium from the 

 apparently uninjured endosporium. The use of reagents, especially Schulze's solution, 

 shows the state of the case to be everywhere as it has been described, and this is 

 apparent in the large spores of Pertusaria even without their use (see the explanation 

 of Figs. 57 and 59 A,B). 



In all cases the spore absorbs 

 water before the commencement of 

 germination, and as a consequence 

 of this it swells and forms vacuoles 

 (Fig. 58). 'If it contains a reserve 

 of food in the form of drops of oil, 

 these are seen to decompose and 

 disappear; the nucleus also becomes 

 indistinguishable. As soon as the 

 germ-tube begins to develope pro- 

 toplasm moves into it from the spore. 

 In many cases the germ-tube grows 

 exclusively at the expense of the 

 protoplasm and the reserve of food 

 in the spore. Germination of this 



kind takes place when water only is present, and succeeds best in water ; examples 

 of it are to be seen especially in Fungi which lead a purely parasitic life, such as the 

 Peronosporeae and Uredineae (Fig. 55); the large spores of Pertusaria, Ochrolechia, 

 and Megalospora are also of this kind. In these cases the spores do not increase in 

 size after the first formation of germ-tubes ; their protoplasm and reserve of food, with 

 the exception of an accidental and unimportant residue, passes over into the tubes in 

 proportion as they develope ; water takes the place of these substances in the original 

 spore-cavity, and the spore-membranes thus emptied of their contents soon perish. 



Other spores require a supply of nutrient substances as well as water in normal 

 germination, or at least absorb them when present. They then increase consider- 

 ably in size and their inner cavity is permanently lined with a layer of protoplasm, 

 like a vegetating cell ; in other words they are permanently vegetating portions of the 

 mycelium that grows out of the spore, and it is not surprising that transverse 

 walls should also be sometimes formed in them. Many Mucorini, as Mucor 

 stolonifer and M. Mucedo, and the Sclerotinieae, as Sclerotinia Fuckeliana, are 

 excellent examples of this kind. Intermediate forms are found, as might be expected, 

 between the two extremes. 



FIG. 58. Helvella escule?ita, Pers. a a ripe ejected ascospore with 

 the two characteristic focal oil-drops, b — e germination of ascospores 

 in water. The stages of the development follow the letters. Magn. 390 

 times. 



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