MR. BERKELKY OX THE rOTATO MURRAIN. 33 



Amongst the diseases noticed by Martins is one which he 

 considers as depending on a species of Protomyces. As I have 

 seen this in various stages of growth and attached to its flocci, 

 I have thought it worth figuring. It appears to me to belong- 

 to the genus Tuburcinia, Fr. The spores have usually one or 

 more cavities in the surflice communicating with the interior 

 cavity. They may perhaps therefore be considered rather as com- 

 pound bodies consisting of a quantit)^ of cells arranged in the 

 form of a hollow ball. This view of their structure requires 

 more attention than I am able to give to it at present. 



I sliall end the memoir by giving the characters, after Dr. 

 Montague, of a highly curious fungus discovered by Dr. Kayer, 

 chief Physician of the Hopital de la Charite, at Paris, during 

 the course of a series of observations on potatoes. It is pro- 

 duced and fructifies in the intercellular passages of germinatinj,- 

 potatoes. 



ARTOTROGUS, Mont. 



Flocci continui ramosi llexuosi per meatus interceUulares vagantes serpentesque. Sporas 

 terrainales vel (ob prolilicationem .-') medio filo insert;c, primo l;cves, splurriccf, rufse, intus 

 farct^>, tandem solutae, libera;, echinulafce. Locus in systemate inter Sepedonium et Tubur- 

 ciniam prope Asterophoram. 



Artotrogus hydnosporus, Mont. — Gard. Cbron., 1845, p. G40. 



Hab. inter meatus cellulares tuberculi Solani tuberosi, germinatione absoluta. 



Kinr/s Cliff e, Nov. 22, 1845. 



Fig. 1. Potato in an eai-ly stage of the disease. 



2. Section of one in which the disease is more advanced. 



3. Small ash-leaved potato, sliowing a concentric arrangement of the 



spots. In larger tubers there are sometimes two systems of con- 

 centric spots. 



4. Vertical section of a small red potato, in which the portion to the 



left has become green externally ; showing the external cells 

 and a few of the internal feculiferous cells (a), some of which at {h) 

 are attacked by the disease, and, in consequence, have their walls 

 clouded with brown specks. The cells immediately beneath the 

 cuticle do not contain fecula, though they sometimes seem to do so 

 under the microscope from stray granules having been introduced 

 -accidentally. Four of the lower cells exhibit Botrytis infestans 

 just commencing. The grains of fecula in the diseased cells 

 are, in this stage of the disease, not diminished in number, but 

 some have escaped in consequence of the division of the cells. In 

 the external cells the cytoblasts are visible at (</), which in the 

 green portion (c) are greatly enlarged, and furnished with radia- 

 ting processes. 

 4.* Appearance presented by healthy and diseased cells when boiled. 



5. Horizontal section of diseased cells (by Dr. Montagne) magnified 



381) diam. The lines on the grains of fecula are omitted, to sim- 

 plify the figure. 

 C. Horizontal section from surface of an apparently sound potato, 

 showing abundant mucedinous threads. This potato, when ex- 

 posed to the sun with a view to observing the changes which take 

 VOL. I. D 



