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BRITISH GALLS 
the only recorded instance of actinomycosis amongst plants. 
The masses of tubercles vary in size from that of a pea to a 
small walnut, but are usually never so large nor so abundant 
as those of the Alder. A single tubercle is a root-like growth, 
branching di- or trichotomously after attaining about 2 mm. 
in length, each tip sending out a thread-like structure, some¬ 
times 3 cm. long, much resembling an ordinary rootlet, 
but tapering towards the tip. It is at first greyish-pink, 
then flesh colour, becoming dark brown when exposed to 
the air; sometimes the tubercles are quite black when very 
old. Mr. William Herridge observed these tubercle masses 
in abundance on the roots of Bog Myrtle in the clay-pits at 
Newton Abbot in 1910, and they are probably of frequent 
occurrence on this plant. 
Fungi that cause reduction in size of the afflicted plants, 
or abortion of certain organs, are termed Atrophytes. With 
such the cecidologist is not concerned, except in a few 
instances in which the dwarfing is accompanied with 
minute gall-like excrescences on various parts of the plant, 
as may be seen in the case of Dandelion plants attacked by 
Synchytrium taraxaci. Under the influence of the parasite 
the dwarfed plants produce minute pustular galls on the 
leaves and involucres. 
Fungi causing enlargement of the entire plant, or hyper¬ 
trophy of certain organs only, are termed Hypertrophytes. 
They may be either autoecious, going through the life-cycle 
on a single host plant, or heteroecious, growing on different 
host plants during the various periods of the life-cycle. 
Amongst the most remarkable of hypertrophies caused by 
fungi on leaves are the cherry-like structures which appear 
in July on the under surface of the leaves of Rhododendron 
fcYYugineum , hirsutum , and Wilsonii , induced by Exohasidium 
rhododendri. The gall is a bullate excrescence, sometimes 
attaining the size of a Walnut, pale at first, becoming reddish 
and shining. It is known as the “ Alpine Rose Apple ” ; it 
superficially resembles the “ Cherry gall” of the Oak leaf, 
but is sweet. This large structure is connected with the 
