184 



COMPARATIVE MORPHOLOGY OF FUNGI 



of the ultimate branches swell and thicken their membranes (Fig. 116, 5). 

 To this first type also belongs Penicilliopsis, whose fructifications are 

 divided into several ascigerous chambers by additional sterile veins 

 differentiated from the ground tissue. 



In the second type, which is only investigated in a representative of 

 the Penicillium "crustaceum" group, the sterile ground tissue first goes 

 through a resting period. About a week after its formation, it thickens 

 its membrane and changes in a stony sclerotium. In its interior lie 

 inconspicuous, aseptate, ascogenous hyphae, recognizable by their more 

 refractive content. 



Fig. 116. — Aspergillus nidulans. 1, 2. Conidiophores with branched phialides. 3. 

 Perithecium, s, surrounded by conidial mycelium. 4. Conidia. 5. Vesicle. 6. Peri- 

 thecium. 7. Section of perithecium; as, ascus; r, rind. 8. Young asci. 9. Germinating 

 ascospore. (1, 2 X 230; 3 X 120; 4 X 1,000; 5, 8 X 400; 6 X 85; 7 X 170; after Eidam, 

 1883.) 



In this condition the sclerotia seem very like the sterile vegetative 

 sclerotia of the other orders and, even in the Aspergillus-Penicillium 

 group, several forms are known whose sclerotia are really sterile and form- 

 ing only a resting condition of vegetative mycelia. Under favorable 

 conditions, they develop directly to a mycelium. If, however, one sows 

 the sclerotia of the above mentioned member of the Penicillium "crus- 

 taceum" group investigated by Brefeld, one observes that only the asep- 

 tate ascogenous hyphae possess life while the sterile ground tissue is 

 passive and gradually consumed by the ascogenous hyphae. About 7 to 8 

 weeks after the sowing of the perithecia, the ascogenous hyphae which 

 extend from the center of the fructification (Fig. 117, F) are divided into 

 short, cylindrical, apparently binucleate cells. Out of many of them 



