358 Miscellaneous. 
and from the adult female, L. ridibundus, in full summer plumage it 
differed in the most trivial manner only. 
ON THE DISEASE OF POTATOES. BY PROF. KUTZING. 
The diseases of potatoes have of late years attained so unusual an 
extent of diffusion, that their investigation must become of universal 
importance, especially when we recollect that this is the only means 
of ascertaining the cause of the disease. 
During the present year a disease has appeared in the potatoes grow- 
ing around Nordhausen with which the author of this communication 
was not previously acquainted; nor is it mentioned in the writings 
which have in modern times treated of the diseases of potatoes. 
It is of a totally different nature from the so-called dry-rot (caries 
of the tubers), in which the starch granules become so altered as to 
exhibit minute brown fungi similar to those of corn-smut, and the 
cellular tissue which surrounds these bodies becomes destroyed or 
dissolved at a subsequent period only. In the disease of the present 
year an alteration and solution of the cellular tissue alone is visible, 
the starch granules remaining within it in a sound and unaltered 
state. For this reason I have called it cell-rot. 
The cell-rot at first appears just beneath the cuticle of the tubers, 
and always extends from thence towards the interior. It constantly 
commences with a brownish discoloration of the substance, which 
at first is still firm and solid, but gradually assumes a lighter and 
darker colour until it is dissolved and forms a greasy, soft, dark brown 
(sometimes verging to violet) mass, which possesses a foetid odour. 
On microscopic examination perfectly healthy starch granules 
may be detected in all the stages of the disease, a proof that the 
true nutritious ingredient is not destroyed by this change. But the 
cells, which contain these starch granules, and which in the healthy 
substance are clear, colourless and extraordinarily transparent, even 
in the earliest stage of the disease appear of a yellowish colour, and 
the membrane exhibits a finely granular structure which impairs their 
transparency. As the disease progresses the colour and granular 
structure of the surface of the cells increase, until at last they are 
either partially or completely dissolved, the starch granules pass out 
of them and become mixed with the decomposed mass. At this pe- 
riod we find in the fluid decomposed cellular mass a fine filamentous 
fungus, which frequently extends to the surface of the diseased cells, 
and is diffused through the soft mass in a ramified form or united 
into bundles. Its formation, as I have satisfactorily observed, is a 
consequence of the decomposition of the cells, for it is not present 
in the earliest stage of the disease. 
The cause of this disease appears to depend partly upon too great 
an amount of moisture, partly on too copious a supply of manure to 
the soil: both induce too rapid a growth of the tubers, which renders 
the formation of a strong and durable cellular membrane impossible. 
Moreover, all the potatoes which have experienced the cell-rot con- 
tain a much lerger amount of aqueous constituents than the sound 
ones. It may be expected that the disease of the tubers which are 
laid up for winter store will extend itself and finally destroy them, 
