Dec. 1898.] BOTANIC.A.L SOCIETY OF EDINBURGH 137 



without any detailed discussion of well-known facts in 

 reference to the forms contained in Loth these orders, that 

 the simplest method of regarding the promycelium is to 

 suppose that it is degenerate, and that it represents a 

 generation which formerly possessed both sexual organs 

 and indefinite conidiophores. 



Basidiomycetes. — Dangeard has demonstrated the occur- 

 rence of fusions between two nuclei in the young basidia of 

 TremcUa, Dacryomyces Calocera, Craterelkcs, Nyctalis, Poly- 

 poms ; and Wager has established the same in Agaricus and 

 Amanita. The resemblance between this phenomenon and 

 that in the two previous classes is obvious. An unbroken 

 series of forms connects the Uredinete with the Basidiomy- 

 cetes. The series commences with plants whose thick- 

 walled teleutospores separate from the mother-plant and 

 rest before germination. The next step in the series is 

 represented by types in which the teleutospores do not 

 rest, but, on the other hand, germinate before being de- 

 tached from the parent; as types of this may be mentioned 

 Coleospormm in the Uredincce, and the Protobasidiomycetes 

 — Auriculariace?e, Pilacrea?, Sirobasidiaceae (4), Tremellaceee, 

 and Hyaloriacete (4), — the basidia of which are septate. 

 The final stage is attained by the Autobasidiomycetes with 

 non-septate basidia. And correlated with the evident fact 

 that the mature basidium represents a promycelium with 

 <jonidia, and consequently that the young basidium is 

 homologous with a spore (teleutospore), we find that the 

 nuclear union takes place in the young basidium. The 

 series traced up from the Uredinefe shows that the basidium 

 represents a degenerate and fructificative generation para- 

 sitic upon its predecessor.^ 



AscoMYCETES. — Dangeard has established the occurrence 

 of a union of two nuclei in the young ascus of Pcziza, 

 Acetahula, Helvella, Geoglossum, Eiirotium, and Exoascus ; 

 Harper's observations have already been noticed earlier in 

 this paper. To trace out the precise evolution of the 

 ascus is not so easy as to follow the phylogeny of the 

 basidium. But in this paper De Bary's view is adopted, 

 that there is a distinct alternation of generations in the 



1 This assumptioa seems iu every Avay more probable tliau the 

 reverse. 



TRANS. BOX. see. EDIN. VOL. XXI. L 



