SummaryMaterial from Colonia Palmarito, Central Trinidad, Santa Clara Province, Cuba, after being kept dried for nearly three years was revived, cultured and studied under laboratory conditions.The material used for the experiments was taken from one of the gross cultures and from pure cultures on cornmeal agar because these cultures had a scanty fringe of conidiophores, leaving a bare surface where perithecia and bulbils formed. Perithecia or bulbils developed in ten days or two weeks after the conidiophores appeared. Conidiophores formed in the gross cultures from dried material in ten days, or in the pure cultures within twenty-four hours after inoculation. More or less luxuriant growth occurred in the cultures, depending upon the substratum and the amount of moisture present.The fungus was identified by Dr. B. O. Dodge asNeurospora crassaShear and Dodge. The conidia were somewhat large for the species but measurements of the ascospores, asci and perithecia which are the distinguishing structures correspond with those described for the type.Formation of bulbils, heterothallism, occurrence of abnormally large ascospores and germination of ascospores from both ends were again noted for the species. Three points heretofore less emphasized were noted, namely, (1) that ascospores even when unheated germinate in three to four hours, (2) that theMoniliastage is positively heliotropic and (3) that the markings on the walls are not“ridges”but lighter differentiated parts of the wall.The ascospores were found resistant to 50°C. although with delayed germination when moist and heated for more than one hour, to 0°C. for two months when frozen in blocks of ice with no delay in germination when returned to room temperature, to—170°to—190°C. for twenty hours when wet and for forty-eight hours when dry with no delay in germination. They were readily germinated at room temperature in three hours without previous heating. The conidia were found resistant to—80°C. for one hour when wet and to—170°to—190°C. for one hour when dry, although killed at this temperature in five minutes when wet. Ascospores that had been confined in an ampule for several days after cooling to—80°C. for an hour or more were found to produce mycelium and spores of two types, normal, small conidia on stunted conidiophores above the water andOidium-like spores below the surface.It is concluded thatNeurospora crassais a generally resistant fungus, not a thermophile requiring heat in its development, but resistant to extreme cold as well as to extreme heat and also to other adverse conditions.In conclusion, I take this opportunity to thank Professor W. H. Weston for supplying the material and for his help throughout the course of the study, Dr. B. O. Dodge for his kindness in identifying the fungus, reading the manuscript and supplying the slide from which the drawing of the cross section of an ascospore was made, and Professor Theodore Lyman for his aid in supplying the liquid air used in the experiments.