Botanical Society of Edinburgh. 275 
the spontaneous separation of the enclosed portion of the cotyledon, 
the testa is frequently found ruptured, but Mr. Griffith does not con- 
cur with Roxburgh in regarding this as the stage of germination, 
which he thinks cannot be said to take place until the radicle has 
elongated and the innermost of the plumulary processes become ex- 
panded. The axis contains the rudiments of additional radicles, 
which after germination become exserted. 
Mr. Griffith thinks that the whole of the anomalies existing in the 
structure of the embryo may be referred to the density of the tex- 
ture of the nucleus and to the shape of its cavity. The direction of 
the radicle appears at first sight to be an exception to a very general 
rule; but this anomaly is proved to take place subsequently to the 
earlier stages of development, during which the apex of the radicle 
corresponds exactly with the apex of the nucleus and with the fora- 
men. He adds in anote that he would limit the expression of the law 
to “‘ radicle pointing or corresponding to the apex of the nucleus,” — 
since there are exceptions to its correspondence with the foramen. 
The perforation of the testa by the radicle is explained by the 
anomalous direction of the radicle in the later period of its deve- 
lopment ; and the separation of the chief part of the cotyledon by 
the constriction exercised upon it by the indurated apex of the nu- 
cleus, Mr. Griffith is inclined to believe from this and some other 
instances that there is no absolute necessity for a cotyledon, but that 
its presence may be supplied by a highly developed plumula; the 
enormous development of the plumula in the present case being evi- 
dently adapted to correct what would otherwise be a destructive 
anomaly. 
Finally, the author adduces the examination of this plant as a 
striking proof of the advantages to be derived from tracing anoma- 
lous forms back to the earliest period of their development. Going 
back to the period immediately before the conical apex of the radicle 
projects through that of the nucleus, we arrive at a stage when the 
form of the embryo closely resembles the usual form of the Aroidee, 
since we have a superior radicle, a cotyledon, and a tendency to the 
formation of a lateral slit, as indicated by the depressed areola. 
BOTANICAL SOCIETY OF EDINBURGH, 
Feb. 12, 1846.—Dr. Balfour, President, in the Chair. 
A large collection of plants from Chippawa, Niagara, and various 
parts of Canada, was presented from Dr. Philip W. Maclagan; and 
specimens of some of the rarer alpine plants of Scotland by Dr. Bal- 
four. 
The following communications were read :— 
1, ‘‘ On the Potato Disease,” by John Goodsir, F.R.S.E., Demon- 
strator of Anatomy in the University of Edinburgh, and Secretary of 
the Botanical Society. 
In reference to the nature of the potato disease, Mr. Goodsir stated 
that there could be no doubt as to its general resemblance to an epi- 
