820 



another cause favourable to their development, and which would ap- 

 pear to have escaped our means of observation. M. Robert believes 

 that the truffles grow at the extremities of the radical fibrillae of trees, 

 and of the evergreen oak in particular, and that they are in nowise 

 connected with the soil. When the vegetative powers of the fibres 

 of the root are quickened by frequent rains, the fibrillae increase in 

 number, and the truffles are found in great abundance. He supposes, 

 from analogy, that the truffles owe their origin to a circumstance 

 nearly similar to that which produces galls and other excrescences 

 upon the leaves of the oak, namely, the puncture of some insect. 

 Two species of truffles are generally known ; one of which is found 

 in summer and autumn, and is pure and white internally, and without 

 perfume ; the other, which is collected towards the end of autumn, 

 during the winter, and in spring, is black, and highly scented. This 

 difference is generally attributed to the influence of the seasons ; but 

 it appears rather to result from the species of tree to which the truffle 

 owes its origin." — Revue Encyclopediqiie, January, 1847. Read be- 

 fore the Academic des Sciences, January, 1847. 



" Truffles are often preyed upon by a species of Leiodes, abundant 

 specimens of which have been collected by Professor Henslow, at 

 Audley End, Essex." — Berkeley in Brit. Flor. v. pt. 2. 



Microscopic and General Observations on the Potato. By Dk. 

 Tyerman. [E.xtr acted from the Fourteenth Annual Report of 

 the Royal Cornwall Polytechnic Society). 



" Having been induced by the conflicting reports respecting the 

 potato blight to make some examination of the plant, both in its na- 

 tural and diseased condition, I have been urged to record the results, 

 and I will also state some of the conclusions to which the investiga- 

 tion has led me. 



" I have unfortunately not seen any microscopic account of the 

 fimgus, or cryptogamic parasite, which causes the decay of the vege- 

 table. I should be glad, however, if in error, to be corrected by any 

 other observer, — the sole motive of this paper being the discovery of 

 the true nature of its subject. I may premise, that having used a 

 compound microscope, capable of high magnifying power, I have not 

 observed any insect, or other appearances than I proceed to describe. 



