CONTRIBL'TIONS FROM THE WlSLEY LABORATORY. 



379 



areas of tissue occupied by the parasite and the unaffected areas is 

 usually very distinct, even in microscopic preparations. The parasite 

 does not during any stage or phase of its life-cycle occur generally 

 distributed throughout the tuber, neither has any evidence been 

 advanced to show that it passes from one part of the plant to another 

 by means of the conducting tissue of the vascular bundles. My own 

 observations seem to indicate that the parasite passes through the 

 several stages of its life-cycle wherever it be found, forming eventually 

 reproductive bodies (spOre-balls). During the period of sporulation, 

 the host-cells containing the parasite rapidly decay. Before accepting 

 the view adopted by Johnson and suggested by Massee, convincing 

 evidence is needed — (1) that the plasmodium of the parasite passes 

 into a resting condition and in this form is able to and actually does 

 hibernate during the winter, (2) that the parasite is able to and does 

 migrate from the diseased set into the young tubers produced by the 

 plants grown from this set by way of the rhizome. 



4 The Supposed Earlier Records of the Occurrence of 

 Spongospora. 



Certain authors claim to trace the discovery of Spongospora to an 

 earlier date than 1886. Massee credits Berkeley with the discovery 

 in 1846. Johnson, on the other hand, believes that Wallroth * was 

 the first to describe the organism in 1842. There is still a third, 

 0. E. P. VON Martius,! who was for some time engaged in investi- 

 gating an epidemic of potato disease in Germany about the time when 

 Wallroth 's technical description of Erysibe subterranea appeared in 

 LinncEa. 



In Berkeley's paper ;[: on the potato murrain, published in 1846, 

 luention is made of a disease known commonly by the name of the 

 scab. This is frequent, especially in calcareous districts. " The 

 surface of the potato being covered with pustules, which at length 

 become cup-shaped, and are powdered within with an olive-yellow 

 meal, consisting of the spores of a fungus." This description is cer- 

 tainly suggestive of potato canker. But whether Berkeley was or 

 was not acquainted with potato canker, does not affect the question of 

 the description of the organism concerned. This must be judged upon 

 its own merits. Berkeley describes the organism as follows:^ — 

 " Amongst the diseases noted by Martius, 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 Tubur- 

 cinia, Fr. The spores have usually one or more cavities on the surface 

 communicating with the interior cavity. They may perhaps there- 

 fore be considered rather as compound bodies consisting of a quantity 



' F. W. Wallhote, Linnaea, xvi., Heft 3 (1842). 



t C. E. P. VON Martius, Die Kartoffel-Epidemie, 1842. 



J M. J. Berkeley, Jour. B.H.S., i. (1846), p. 9. 



