HYPOCREALES 



233 



trichogyne fertilization known at present, that of Monascus, is easily 

 connected to the relations predominating in gametangial copulation. 

 The second group of the Hypocreales, that of the Didymosporae 

 (ascospores two celled), Phragmosporae (ascospores three or more celled) 

 and Dictyosporae (ascospores muriform) is the largest in species and 

 most important for plant pathology. The representatives here discussed, 

 as those of the Amerosporeae, may be divided roughly into three stages : 

 a first in which generally a stroma is lacking and the perithecia, as in 

 Neocosmospora and the simpler species of Melanospora, rest singly on the 

 substrate; a second stage, in which they are joined into pulvinate undiffer- 

 entiated stromata; and a third in which the stromata are differentiated 

 in an unknown manner and change into characteristic fructifications. In 

 order better to survey these (ideal) stages and their representatives, 

 they are presented in the following table (after Moller) ; for comparison, 

 the genera of the Amersporeae have been included. 



Diagram XXIII. 



We will discuss as representatives of the first stage, four hemisapro- 

 phytic, hemiparasitic (often weak, or wound parasites and thus important 

 for plant pathology) genera : Nectria of the Didymosporae, Calonectria and 

 Gibberella for the Phragmosporeae and Pleonectria of the Dictyosporeae. 



As in the Aspergillaceae of the Plectascales, the color of the mycelium 

 is largely dependent on the nutrition, especially on the reaction of the 

 substrate. Thus the olive green to brown mycelium of Nectria Ipomoeae 

 on alkaline media becomes red on acid media; the red mycelium of Gibberella 

 Saubinetii on alkaline media becomes yellow on acid, and the blue 

 mycelium of Fusarium orthoceras on alkaline media, becomes red on 

 acid. As the hyphae in a few Plectascales, the germinating ascospores 

 of a few forms of this group, as Nectria sinopica, may develop by sprout- 

 ing under certain nutritive conditions. In some other forms, as N. 

 inaurata on the dry branches of Ilex aquifolium and N. Coryli on Corylus, 

 Salix and Populus, this sprouting of the ascospores may begin in the ascus 

 (Fig. 150, J), whereby the asci may be entirely filled with a sprout 

 mycelium, as in Taphrina (Brefeld, 1891). 



