364 ON THE STUDY OF MICRO-FUNGI. 



growths, so that in course of time it will be found that even when 

 walking quickly along a road or over a field, the suspicious-like 

 appearance of a plant or a small coloured spot upon a leaf will 

 often arrest the attention of one who is familiar with such signs. 



We remember that upon one occasion, when hastily cross- 

 ing a field, a slight yellow coloured spot on a leaf of the common 

 daisy was sufificient to cause a halt in order to see what was the 

 reason for the discoloration It turned out to be the Cluster Cup 

 Fungus (^cidium bellidis)^ and although a considerable search 

 was made, no more than three very small diseased leaves could be 

 found. This habit of always looking for diseased plants grows 

 upon one, so that no matter how beautiful the flowers and sur- 

 rounding vegetation may be, the eye is continually wandering 

 about in search of any sign which betokens the presence of a 

 fungus ; and, although it may sound strangely to the uninitiated, 

 the joy is much greater when the plant is found to be attacked by 

 one of these parasites than when it is in the full vigour of health. 



It is not always easy, by a cursory examination, to distinguish 

 those marks which are caused by fungi from those which are due 

 to insects or the natural decay of the tissues of the plant ; indeed, 

 until the microscope has been brought to bear upon them, it is 

 sometimes almost impossible to settle the question with certainty. 

 The common dock by the wayside is a prominent offender in this 

 respect, as the leaves are very frequently marked by coloured 

 spots, which prove an abundant source of disappointment, until 

 the collector is rendered wary and taught not to expect too much 

 from them. Mistakes of this nature, however, become fewer as 

 the observer becomes more familiar with his subject. 



The majority of the species must be looked for on the under- 

 surface of the leaves, and there will be found to be a great diver- 

 sity, not only as regards the microscopical appearance of the 

 different spores, but also as regards the appearance which they 

 present to the naked eye, both in colour and in the manner of 

 their growth on the host plant. The beautiful cluster cups, to 

 which we shall refer more particularly further on, will, on some 

 plants, be seen in clusters, on others in circles, and on others 

 scattered about in no apparent order or running down the leaf- 

 stem, as is frequently seen on the Violet ; while on the Willow 



