ON THE STUDY OF MICRO-FUNGI. 373 



When these different plants are examined in about a fortnight, 

 no change will be observed in the Lapsana which was not inocu- 

 lated, nor will there be any signs of fungus on either the Daisy or 

 the Nettle ; but on the Lapsana, on which were placed the secidi- 

 ospores, there will be seen a quantity of very small light-brown 

 spots. These spots on examination with the microscope will 

 resolve themselves into sori or clusters of spores. They form, 

 indeed, the next stage in the life-history of the fungus we are 

 considering, and are termed uredospores. These uredospores are 

 the product of the mycelium formed by the development of the 

 germ tubes of the secidiospores. The mycelial tubes accumulate 

 in special centres, and from these parts there are branched off 

 large numbers of upright hyphae. At the apices of these hyphae 

 the uredospores ate formed, w^hich when ripe become separated 

 from the hyphae, in order that others may be developed in the 

 same way. The growth of the fungus at length breaks through 

 the leaf, and the ruptured epidermis can often be plainly seen 

 around the sori. 



When the uredospores are separated from the beds on which 

 they have been produced, they usually become detached, not 

 exactly at the junctions between the spores and the hyphae, but at 

 a short distance below them. The spores are then free and ready 

 to be dispersed with the first breath of wind. The sori or spore 

 clusters, which are scattered over both sides of the leaves, are not 

 nearly so prominent and easily discovered as the previous stage of 

 the fungus, neither are the leaves distorted by the presence of the 

 mycelium as we saw they were when the aecidium was being 

 developed. The spores themselves are ovate, of a brownish colour, 

 about 1 8 micro-mm. in diameter, and are covered with short, 

 sharp points or spines. They will, of course, be found on the 

 Lapsana immediately after the aecidiospores, say, during the months 

 of April, May, and June, and if we obtain, as we did with the 

 previous spores, some of the ripe uredospores, we shall find 

 that, when placed in water, they will germinate in precisely the 

 same way. 



In a few hours after immersion the germ tube will have been 

 extended through one of the germ pores in each ripe spore, and 

 the protoplasm and colouring matter transferred from the interior 



