34 
posed of a bright brown parenchyma, on which stand numerous 
conidia having colorless, unicellular and very slender stems, about as 
long as themselves. The conidia are small, cask-shaped, about one- 
third of a millimetre in length, and usually divided by slightly con- 
stricting septa into four cells, of which the two terminal are longer 
than the two middle ones. From these cells germinal filaments may 
proceed, from which are developed brown, thick-walled and many- 
celled mycelia. The first symptom of the gum disease is the develop- 
ment of a beautiful red color around the wound, due to the formation 
of a red pigment in one or more of the layers of the cells of the bark. 
Dr. Beijerinck believes that the fungus produces a fluid of the nature 
of a ferment, which penetrates the adjacent structures, since the dis- 
ease extends beyond the parts in which any trace of the fungus can 
be detected. This ferment he believes to act on the ccll-waJls, starch 
granules and other constituents of the cells, transforming them into 
gum and even changing into gum the Coryneum itself. The influence 
of this fluid is also exerted in the cambium, causing the formation of 
morbid parenchyma, the cells being cubical or polyhedral, thin-walled 
and rich in protoplasm w^hich is in its turn transformed into gum. It 
is further stated that ** a similar disease produces gum arabic, gum 
tragacanth, and probably many resins and gum-resins." Gum tra- 
gacanth is known to be produced by the pith as well as the bark of 
the stem, and to ooze out from the pith when the stem is cut; and if 
it be indeed due to a disease it would seem as if the disease infects 
the whole plant. Gum, moreover, may be found in the uninjured 
husk of the almond, and it seems at first sight more probable that 
the irritation caused by a fungoid parasite should cause a greater 
flow of the natural product, just as the irritation caused by an insect 
causes the development of galls 
Tuberous Species oj Solanuni, — A paper upon this subject was read 
by J. G. Baker at a meetin'g of the Linnean Society on January 17th. 
There have been about nine hundred species described as belong- 
ing to the genus, which, however, Bentham and Hooker would re- 
duce to about seven hundred. Only a very small proportion of these 
has tuberous underground stems, this section including, according to 
DunaKs monograph in De Candolle's ' Prodromus,' twenty species, 
all natives of the South American continent, and as far north as Mex- 
ico and Texas. These twenty species Mr, Baker thinks should be re- 
duced to six, with well-marked specific characters. While, from a 
botanical point of view, the range of Solaniim tuberosum has been un- 
duly narrowed by separating from it forms which are not specifically 
distinct, from a popular point of view it has, on the other band been 
erroneously extended, from the fact that the late Mr. Darwin, in his 
' Voyage of the Beagle,' described the potato as growing as far south 
as 50"* S. lat. But Mr. Baker has clearly determined that the species 
gathered there by Mr. Darwin was not Solanum Uiberosiim, but a quite 
distinct species, S, Maglia. The geographical range of the trae^. 
tuberosum extends from Chili to Mexico, though it is doubtful to what 
exten 
time immemorial by 
Magli 
LtlilC IllllllClllUl lai U^ lilt- i-iiuiciuo. -^-w^. ^. "^ , J 
portant of the tuberous species are 5. Commersoni, widely dispersea 
