78 DIVISION I. GENERAL MORPHOLOGY. 



transverse zone lying in the middle of the ascus, or in most other species into a mass 

 which fills the upper third or fourth portion of the ascus ; the remaining and especially 

 the lowermost portion contains only the glycogen-mass which is marked by many 

 vacuoles of varying size and arrangement. Sometimes, as in Morchella esculenta 

 and Peziza Acetabulum, the uppermost portion of the ascus above the protoplasm is 

 occupied by a layer of glycogen, the protoplasm filling a cavity with a sharply 

 defined outline in the glycogen-mass. The nucleus always lies in the protoplasm and 

 in or near its centre, at which point the spores are formed in these as in other species, 

 the mode of formation being essentially the same as that described above. The young 

 spore-primordia are in contact with one another in Peziza convexula and Morchella 

 esculenta. Only the first stage in the division and the ultimate eight nuclei, round 

 which the formation of spores takes place at once, have been directly observed in 

 most of the above species; the other stages have been seen only in Peziza convexula. 

 But the accounts which we possess and observations on the formation and division 

 of nuclei in other plants compel us to assume, that the process in the eight-spored 

 ascus are essentially the same in all cases and that the successive stages in the division 

 of the nucleus have simply been overlooked, owing partly to the rapidity with which 

 the operation is effected and partly to difficulties of observation of other kinds. 



Numerous independent observations on a considerable number of Discomycetes with 

 eight spores formed simultaneously in one ascus have established the presence of 

 the primary nucleus before the formation of spores, the appearance of the young 

 spores in the manner just described, and the occurrence or non-occurrence of differen- 

 tiation of the glycogen-mass and protoplasm according to the species. There is therefore 

 no reason to doubt, that the course of development above described prevails very 

 generally in the group which contains the genera Peziza, Phacidium, Leotia, Ascobolus 

 and Geoglossum. It is often difficult to follow it throughout in large asci, like 

 those of Leotia lubrica, Geoglossum hirsutum, Helvetia, &c., because the protoplasm 

 of the young tube and of the spores is rendered opaque by the number of drops of 

 oil. In very many other cases the minuteness of the asci and spores either prevents 

 a complete observation or renders it difficult ; but even in these cases a little attention 

 will enable us to see the primary nucleus, the simultaneous appearance of the eight 

 spores as portions of protoplasm with a fine boundary-line, and sometimes (Sclerotinia 

 sp.) a nucleus in each of them. In the small asci of e.g. Peziza tuberosa, P. Sclerotiorum, 

 P. calycina and Phacidium Pinastri, and also in some larger ones, as those of Lecidella 

 enteroleuca, Pertusaria lejoplaca, Lecanora pallida and Sphaerophoron coralloides, 

 the primary nucleus appears as a strongly refringent roundish body, which is either 

 homogeneous or more pellucid and as if hollowed out in the centre ; the clear, trans- 

 parent, spherical space is not or not always (Peziza Fuckeliana) to be seen through the 

 periphery. 



It is more difficult to observe the formation of the spores in the asci of the Pyreno- 

 mycetes containing eight spores formed simultaneously, than in the Discomycetes, 

 on account partly of the minuteness and delicacy of the organs, partly of the presence 

 of oil globules which are present usually in large numbers in the protoplasm. Yet 

 careful observation shows that the spores are formed in the way described above. 

 A nucleus has rarely been seen in them (Sordaria fimiseda, Fig. 52). An oil globule 

 was often taken for a nucleus by older writers. The primary nucleus on the contrary 

 may be distinctly seen in many species before the spores are formed ; it has the 

 characteristics of the nucleus of Peziza calycina and P. tuberosa which have just been 

 described, and always lies in the same position a little above the middle of the ascus, 

 for example in the nuclei of Xylaria polymorpha, Nectria, Sphaeria obducens, 

 Curcurbitaria Laburni, Pleospora herbarum, Sordaria fimiseda, De Not., and some 



