ON THE STUDY OF MICRO-FUNGI. 379 



those already recorded as occurring on the Phalaris. It certainly 

 is very remarkable that, although they all find a congenial home 

 on the Phalaris and do not differ microscopically very much from 

 each other, yet each has its own particular host on which to spend 

 the first part of its life. 



In order to understand how the Herb Paris becomes infected 

 in a state of nature, it is only necessary to remember that the 

 withered grass bearing the Puccinia was found lying on the ground 

 directly over the area where the Herb Paris was growing. The 

 young plants, therefore, required literally to push aside the fallen 

 grass in order to get space to grow, and multitudes of the teleuto- 

 spores would consequently be encountered both on the ground 

 and on the grass. The spermogonia were soon followed by the 

 secidia, that is the cups containing the secidiospores. The cups 

 are developed on the under surfaces of the leaves, hypophyllous, 

 and are arranged generally in the form of small circles. See PI. 

 XVII., Fig. 6. The circles, which are usually very definite, are 

 formed by a single row of peridiae or cups, with a vacant or clear 

 space in the centre. The places on which the aecidia grow, and 

 for a short distance round the margin of each circular spot, are 

 lightish coloured, owing to the chlorophyll being destroyed by the 

 fungus. The number of such circles of cups on each leaf does 

 not very often exceed two or three, but a leaf may occasionally be 

 found bearing five, six, or even more of them. 



Having thus proved the case so far, the next step was to try 

 the reverse culture, to see if the secidiospores, when sown on the 

 Phalaris, would produce the uredospores. This was accordingly 

 done and also proved successful, for in about three weeks the 

 desired spores made their appearance on the grass. The sori or 

 spore clusters are small, of a reddish yellow colour, and were deve- 

 loped in fair abundance on both sides of the leaves. The spores 

 are globose, finely echinulate, and measure in diameter 30 — 35 

 micro-mm. In a state of nature, the Phalaris becomes infected, of 

 course, from the spores which are blown on to it from the Herb 

 Paris, and if there be moisture on the grass they straightway emit 

 the germ-tubes, which enter into the tissues in the usual way. 

 The uredospores are usually to be found in the month of July. 

 When they are ripe, they also germinate, and very shortly the 



