Mesospores and Amphispores. 



CHAPTER VIII. 



MESOSPORES AND AMPHISPORES. 



In the great majority of Australian Puccinias, 80 per cent, at least, 

 there occur associated with the teleutospores, and quite distinct from the 

 uredospores, unicellular spores which somewhat resemble the two-celled 

 spore in coloration, though generally much paler. It is generally notice- 

 able that wherever the teleutospores are thickened, or apiculate, or pro- 

 longed into processes at the apex, or warty on the surface, these spores 

 possess the same characteristics. The conclusion one would naturally draw 

 is that they are teleutospores in the process of making, with t'Jie lower 

 cell wanting, just a survival of what is normal in the Uromyces. From 

 their partaking of the nature of a middle spore-form between Uromyces and 

 Puccinia, they are gent-rally called mesospores, and simply represent an 

 imperfectly developed or abortive teleutospore, which may, however, in 

 certain cases perform the functions of a fully-developed teleutospore, 

 although only one-celled. 



In the newly-constituted genus Uromycladium there are found in con- 

 siderable numbers among the uredosori, smooth- walled spores smaller than 

 the uredospores, produced singly on basidia and entirely different from the 

 teleutospores, to which the term mesospores has also been applied. 



Just as there are two kinds of teleutospores, so there may be two kinds 

 of uredospores, which are represented at present in a few species (belonging 

 to Uromyces and Puccinia, but have not hitherto been found in Australia, 

 This modified uredospore, while agreeing with the normal uredospore in 

 the mode of germination, possesses a thickened epispore, and a more or 

 less persistent pedicel. From its partaking of the characters of both 

 spores, those of the uredospore in its possession of two or more germ-pores, 

 and those of -the teleutospore in its germinating only after a period of rest, 

 it has been called an Amphispore, by Carleton. 



AMPIII SPORE. 



This peculiar kind of spore was first investigated in connexion with 

 Puccinia vexans Farl. This species has a true uredo and teleuto-stage, 

 in addition to a third form of unicellular spore, and the latter was the first 

 to be recognised and recorded. In 1879 it was described as Uromyces 

 brandegei by Peck, the unicellular spores being rough with minute warts, 

 and therefore suggestive of Uromyces. Then, in 1883, Dr. Farlow 1 

 found true bilocular teleutospores associated with the supposed Uromyces, 

 and named the fungus Puccinia vexans, the specific name referring to the 

 perplexing nature of the unicellular spores. As Dr. Farlow writes: "The 

 perplexing question arises, are the one-celled spores a unilocular form of 

 teleutospores similar to what is known as P. cesatii, Schr., or are they ,the 

 uredospores of this species?" Their true nature was finally settled in 

 1897, when Carleton succeeded in germinating them, and ultimately they 

 were found to give rise to two germ-tubes, as in the true uredospore which 

 had been discovered the previous year. Now that the three spore-forms 

 are known in this species, it becomes possible to answer the question, in 

 what respect does the amphispore differ from the teleutospore, on the 

 one hand, and the uredospore on the other. It agrees with the uredospore 

 in being unicellular, and having more than one germ-pore, but differs in 



