44 



MORPHOLOGY AND CULTURE OF MICROORGANISMS 



whom is Arthur Meyer, believe them to consist of a combination of 

 nucleic acid, but this is a mere supposition. 



- On the other hand, the r61e of the metachromatic corpuscles is now 

 well known. It is evident that they are reserve substances. Their 

 evolution proves it. Thus metachromatic corpuscles appear in great 

 abundance in the young asci of the higher Ascomycetes (Fig. 28, i and 

 2), then accumulate in the cytoplasm of epiplasm 

 which is not utilized in the* formation of the 

 ascospores, gather all around the ascospores at 

 the time of their forming (3-4), and are gradu- 

 ally absorbed by the latter in the course of 

 their development (5). They therefore furnish 



Fig. 27. Fig. 28. 



Fig. 27. — Demaiium species Stained by a method permitting the differentiation 

 of the metachromatic corpuscles, i, Filament. 7 and 9, Yeast forms. 9, Yeast 

 form starting to bud from mycelium. The metachromatic corpuscles are situated 

 in the vacuoles in the form of small grains joined in chains (6) or isolated. Many 

 appeer like large granules (9). n. Nucleus, v.c. Vacuole with metachromatic 

 corpuscles. 



Fig. 28. — Various stages of the development of the ascus in Aleuria cerea. 

 I and 2, Young asci with their nucleus and many metachromatic corpuscles. 3, 

 FragDients of an ascus after the second nuclear division. 4, Ascus, still young, 

 in which the ascospores are surrounded by metachromatic corpuscles, j, Older 

 ascus in which most of the metachromatic corpuscles have been absorbed by the 

 ascospore^. 



nourishment for the ascospores and from this standpoint behave 

 exactly like glycogen and the globules of fat which are usually coexistent 

 with them in the cytoplasm. We shall see, moreover, that they 

 undergo a similar evolution in the asci of yeasts. Likewise in the coni- 

 diophores of molds, notably in the fruiting heads of Aspergillus and 



