MONOGRAPH OF THE LABOULBENIACEyE. 



241 



teen days, according to the temperature at which they were kept ; and it is certainly 

 improbable that many forms attain maturity in a much shorter period than this. 



In regard to the longevity of individuals, it seems quite certain that those which 

 have been mature in the autumn, may still produce spores during the spring and early 

 summer ; for although mature specimens which have hibernated are apt to be much 

 damaged, and are often no longer fertile, fully mature individuals, evidently of consid- 

 erable age, from their dark color, have been found on hosts still hibernating and col- 

 lected by " sifting " early in the spring before the advent of warm weather. That 

 the germinating spores and young individuals live over winter, attached to their hosts, 

 in a dormant condition, is an undoubted fact ; and it is upon the survival of these, 

 rather than on that of the maturer individuals, that the fungus depends for its perpet- 

 uation. That a majority of forms, occurring in temperate climates, live throughout 

 the summer and early autumn cannot be doubted ; since one very rarely finds individ- 

 uals that are old and infertile. When such cases occur, with few exceptions (as in 

 Amorphomyces), the cessation of fertility has evidently resulted from some violent 

 injury which has destroyed the perithecium, or a portion of it. From my own obser- 

 vations in this connection, I think that it may be safely assumed that, in a majority 

 of cases, the life period of the parasite coincides with that of the host. The number 

 of spores formed by a single individual must therefore be often enormous, in view of 

 the fact that the ascogenic cells are continuously active during the growing season. 



Geographical Distribution. Any intelligent discussion of the distribution of 

 the Laboulbeniaceee is hardly possible, since it is in North America only that their sys- 

 tematic study may properly be said to have commenced; yet, judging from the small 

 number of exotic hosts which have been available for examination in connection with 

 the preparation of the present monograph, it may be inferred that the warmer portions 

 of the earth are quite as rich in representatives of the group as are the more temper- 

 ate regions, while towards the colder northern latitudes they become distinctly less 

 abundant. For, although specimens have been examined from localities as far north 

 as Hudson's Bay and the Aleutian Islands, a comparatively small percentage of the 

 hosts collected in these regions appear to be infested, while the reverse is true as the 

 southern portion of the United States is approached. Notwithstanding the fact that 

 the Carabidoa and Staphylinida3, families of beetles which furnish by far the majority 

 of the hosts at present known, are relatively much less abundant in tropical than they 

 are in temperate regions, it seems highly probable that, in such localities, these orders 

 are replaced by numerous other insects having suitable life-conditions, among which 



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