DISEASES OF FERNS. 
73 
pteris, etc. The second is black like a small bead, fixed 
by its neck to the substance on which it grows ; it only 
infests dead stems of Pteris aquilina ; its name is Do- 
thidea filicina . The third is a still smaller enemy, not 
larger than a pin point; the Pteris is its favourite 
home, and you may take up dead fronds in the woods, 
and find the stem and rachis speckled all over with 
thousands of Sph&ria pant her ina* These two last, seeing 
that they infest only dead stems, and those the stems of 
the most abundant of our wild ferns, are not enemies 
to cause much anxiety, and do not necessitate the call- 
ing out of a volunteer force for protection. 
The greenhouse and hothouse ferns have fierce enemies 
in small insects called by gardeners thrips, and scale- 
Syringing is the best safeguard against the appearance 
of these foes ; but when they have effected a settlement 
they can only be dislodged by thorough fumigation and 
careful washing with a decoction of tobacco and sulphur. 
When the insect called “ mealy bug ” appears, there is 
no cure but fumigation. 
