-6 Origin of Spore-forms. 



It is worthy of mention that Magnus 2 has repeatedly obsewed 



that when the teleutospores of Puccinia graminis were germinated in water 



te- produced an undivided germ-tube just like that of a uredospore, but; 



he could not satisfactorily settle the question, if this germ-tube could directly 



a thick to a thin wall, from one to a number ol 

 germ-pores, and from a typical promycelium to an ordinary germ-tube, has 

 been shown, and it all tends to support the view that the uredospore may 

 have been derived from a teleutospore. 



This peculiar germination of the teleutospore, in which e'ach promy- 

 celium breaks up into three or four detached cells', apparently representing 

 sporidiola, had been observed by Barclay' as early as 1891, in -P^cirna 

 firainiana, Bard, and Uromyces solidaginis, Niessl. He considered this 

 abnormal mode of germination to be due to the restricted supply of air 

 obtained bv the spores in a hanging drop of water, for, when allowed to 

 germinate in a watch-glass of water, with freer access of air, the germina- 

 tion was normal. 



But this rounding off of the promycelial cells may be due to the influ- 

 ence of micro-organisms in the water. So far as our own observations 

 go, certain organisms are always present in great abundance when this 

 rounding off of the cells occurs. A similar phenomenon is observed ^n 

 connexion with the hyphae of numerous fungi growing in water or fluids 

 invaded by bacteria. 



In another respect the uredospores show a distinct transition. In a 

 \vell -developed spore-layer they always precede the associated teleutospores, 

 but in Uromyces scutellatus', as Magnus 2 has repeatedly observed, in 

 different years they may appear simultaneously. 



The uredospores 1 may thus be regarded as having been derived from 

 the teleutospores, or from a mycelium common to both, and the question 

 naturally arises as to the origin of the aecidios pores. 



AECIDIOSPORES. 



Aecidiospores and uredospores are often so much alike that they are 

 mistaken for each other, and sometimes there is a difference of opinion as 

 to whether a spore-form should be regarded as one or the other, as in 

 Triphragmium ulmariae ; but, generally speaking, aecidiospores are produced 

 in chains, and uredospores singly on evident pedicels. In Coleosporium and 

 Chrysomyxa, however, the uredospores are developed in chains as well as 

 the aecidiospores, and this renders necessary the further distinction that the 

 aecidiospore always precedes the uredospoie in point of time. 



In Phragmidium subcorticium, for instance, the aecidiospores were not 

 recognised at first as distinct from the uredospores, but although the indi- 

 vidual spores resemble each other closely, the fact that one is produced in 

 chains and the other not, distinguishes them. When aecidiospores are pro- 

 duced without any special envelope or pseudo-peridium, as it is called, it 

 is distinguished from the Accidium proper as a Caeoma, and there is every 

 gradation from naked to covered aecidia. In Chrysomyxa the uredo is re- 

 garded as a caeoma-form by Raciborski but in Phragmidium the aecidio- 

 spores are protected by a dense layer of paraphyses, which surround them, 

 and thus take the place of a peridium. Triphragmium ulmariae (Schum.) 

 Link, has what are called primary and secondary uredospores, although 

 the former are described by De Toni as aecidiospores, but they are not pro- 

 duced in chains. Winter regards them as biological representatives of the 

 aecidium, and Drs. Milesi and Traverso l speak of them as epiteospores, to 

 distinguish them from caeomospores, which are arranged in chains. There 



