16 MICBOSCOPIC PTINGl. 



named Mddhim Thesii, but which is far from nncom . 

 mon on the Continent. It occurred in this instance 

 on the Downs, in the vicinity of Winchester. 



It is unnecessary here to refer to other allied 

 species of Mcidium, except one to be pre- 

 sently noticed, since we have, at the end of 

 the volume, enumerated and given descriptions 

 of all the species hitherto found in Britain. 

 Suffice it to say that the Buckthorn cluster- 

 cups on the alder buckthorn {Bhamnus fra/n- 

 gula), is usually very common in the Highgate 

 and Hornsey woods, and on the common buck- 

 thorn [JRhmn/nus catJia/rticus) in the neighbourhood 

 of Dartford, in Kent. That on the honeysuckle we 

 have found but very rarely. On the gooseberry 

 and red-currant leaves, commonly in some years 

 and rarely in others ; whilst a few of those de- 

 scribed we have never collected. The species on 

 different composite plants is subject to great vari- 

 ation, and on most may be found in the autumn ; 

 one variety only, on the leaves of Lapsa/tia commmms, 

 we have raet with in the spring. 



Very few years ago farmers generally believed 

 that the cluster-cups of the berberry {Berberis vul- 

 ga/ris), were productive of mildew in corn growo 

 near them; this opinion even received the sup- 

 port of Sir J. Banks, and recently it has been 

 revived amongst botanists, but is not absolutely 

 accepted, as not wholly proven. In this instance 

 the cups are much elongated, and cylindrical ; 



