68 DIVISION 7. GENERAL MORPHOLOGY. 



The spore-formation in Ustilago and Geminella, which will be further considered 

 in section LV, appears from Winter's observations on Geminella and Ustilago 

 Ischaemi J to be nearly allied to the cases just described. More certainly is this the 

 case with many acrogenously formed so-called septate spores, as those of Puccinia 

 (Fig. 26 /) and Phragmidium, and many forms of Hyphomycetes, the systematic 

 position of which has not yet been exactly determined, Trichothecium, Arthrobotrys 

 Fusiporium, &c.; also forms which we now knowas gonidiophores of the Pyrenomycetes, 

 such as Fries' groups of the Dematieae and Sporidesmieae, Helminthosporium, 

 for example, Cladosporium, Alternaria, Sporidesmium, Phragmotrichum, Polydesmus, 

 Melanconium, Stilbospora, Coryneum, Exosporium, and very many other forms. See 

 Figs. 21 and 34, and section XXIX. 



SECTION XVII. The inception (Anlegung) of acrogenously produced spores 

 takes place in every instance according to one or other of the processes which have now 

 been described. In some also ripeness, that is the capacity for further normal develop- 

 ment, and the size, form, and structure which indicate this capacity, is reached, as has 

 been repeatedly stated above, when the delimitation is completed. This is the case, 

 for example, in Corticium amorphum (Fig. 30) and in many, perhaps in all the 

 BasSdiomycetes, and to a certain degree in Cystopus Portulacae (Fig. 33) ; in the 

 case of many other small spores attached by a very narrow stalk it is not possible to 

 speak with certainty on this point, because the minuteness of the point of insertion 

 renders it impossible to determine the exact moment when delimitation by the cross 

 septum is effected. On the other hand, many cases are known in which after acro- 

 genous delimitation the cross septum undergoes a considerable amount of growth before 

 it is mature, and it obtains the necessary food for this purpose from the sporophore ; 

 this is the case, for example, in all the species of the Uredineae mentioned in the pre- 

 ceding sections, and in Eurotium and Penicillium, &c. In a rapidly growing successive 

 chain in these species the majority of the younger members are still immature, and 

 the nutrient material, so far as it comes from the sporophore, must pass by the younger 

 cells to reach the older more distal ones. 



. Many acrogenous spores are persistent on the sporophore after they are mature, 

 and are carried away from the place where they were formed only by accidental 

 external mechanical agencies, as the teleutospores of Uromyces, Puccinia, and 

 Phragmidium, the large gonidia of Hypomyces and many other septate forms above 

 mentioned. 



But the larger part of these spores are detached from the sporophore as soon as 

 they are mature by the aid of internal causes, which during the process of ripening 

 bring about certain changes in the original condition and thus render the ultimate 

 separation possible. The three chief modes known to us in which this purpose 

 is effected are the disappearance of the sporiferous structure (Schwinden der Trager), 

 abscision * (Abschniirung), and abjection s (Abschleuderung). 



The disappearance of the sporiferous structure is most common among the 

 Gastromycetes, in which, when the spores are ripe, not only the basidia, but usually 



1 Flora, 1876, Nr. 10, n. 3 See note on page 61. 



3 See note on page 84. 



