74 



§m&mt& Jttonthlg. 



subject. I purpose in this article, Mr. Editor, to 

 give some of my own observations and experience 

 touching the question, — hoping I may excite the 

 criticism, if nothing more, of those who may have 

 approached nearer a solution of the problem than 

 my very limited abilities have permitted. 



What, in the first place, are the leading theories 

 as to the cause of blight? 



The prominent one is that advanced by the late 

 A. J. Downing, designated the "frozen sap" theory. 

 According to this author (excellent authority, gen- 

 erally,) blight in the Pear tree originated as follows : 



A dry summer occurs, completing the (first) 

 growth of the trees early; a damp and warm Fall 

 ensues, which forces them into a vigorous second 

 growth, continuing late ; in this condition, the sap 

 vessels being filled with their fluids, an early winter, 

 or a sharp and sudden freeze (which is, perhaps, re- 

 peated several times,) occurs at night, followed next 

 day by a bright sun ; the descending currents of sap 

 becomes thick and clammy, chokes up the sap ves- 

 sels, freezes and thaws again, loses its vitality, be- 

 comes dark, discolored and poisonous, lodges along 

 the inner bark, and remains thick and sticky all win- 

 ter. In the ensuing spring, the sap rises through 

 the alburnum ; leaves and new shoots put forth, and 

 the tree appears flourishing for a time. Early in 

 summer, however, the descending sap mixes with 

 the poisonous sap lodged along the inner bark, di- 

 lutes it, and the poison is carried into the branches 

 and body of the tree, causing death, wholly or par- 

 tially. The disease, according to Mr. D., origina- 

 ted in the autumn previous to the death or injury 

 of the tree. 



On looking among other authors I find that Mr. 

 Field, as to the cause of the disease, coincides sub- 

 stantially, though not wholly, with Mr. Downing. 



Mr. Barry does not appear satisfied with any 

 theory thus far proposed. Mr. J. J. Thomas re- 

 fers the cause to "changes of temperature acting 

 upon trees possessing some unknown affection or 

 predisposition to disease." And this is about the 

 status of the question among authors. 



Another gentleman, of scientific attainments. 

 Prof. J. H. Salisbury, of Cleveland, has recently 

 given to the public the result of a series of micro- 

 scopical examinations, made by him in 1862, in cen- 

 tral Ohio, upon Pear, Apple and Peach trees af- 

 fected with blight. (See Ohio Agricultural Re- 

 port, 1863.) 



After numerous critical examinations, with a mi- 

 croscope of high power, he arrives at the conclusion 

 that the disease is produced by a parasitic 

 or cryptogamic plant, which not only poisons the tis- 



sues of the tree, but extracts their juices and vital- 

 ity. The plant, he says, is found vegetating most 

 abundantly in low, rich, peaty, boggy grounds, and 

 in other localities of similar character, when broken 

 up for cultivation or other purposes, and lying in a 

 drying state. The spores (seeds) of this fungus are 

 produced in countless myriads, and, being infinites- 

 simal, are taken up in the cool, heavy fogs and va- 

 pors arising at night from the grounds, wafted by 

 slight currents to other and higher positions, (gene- 

 rally upon, and, for a short distance, above, the 3d 

 terrace from the stream bottoms — which corresponds 

 with the line of suspended stationary fogs and va- 

 pors,) and are there suspended in these exhalations 

 until after sun-rise, and in contact with, and among 

 growing fruit and other trees. Thus immersed, the 

 the trees inhale or absorb, through their stomates, 

 these miasmatic spores in great quantities, which 

 are thereby introduced in the sap or circulation of 

 the tree, and become, in many instances, fixed in and 

 along the soft and juicy tissues. Here they vege- 

 tate, and rapidly spread their mycelium (roots) 

 through the soft wood and bark, or cambium, and, 

 by their poisonous" impressions and absorption of 

 the juices of the tree or limb, for their own sus- 

 tenance, soon cause death to the part affected. — 

 This is the theory advanced by Prof. Salisbury, as 

 nearly as I can glean it from the unarranged mass 

 of material given by him to the public. 



Having been the discoverer of this microscopic 

 fungus. Prof. S. names it Spoerotlieca pyrus, from 

 its disposition to affect the Apple and Pear trees. 

 Another variety of fungus, of perhaps the same spe- 

 cies, ascertained by him to be the cause of rot in 

 the Pear fruit, he names Mucor nigricous, from its 

 black appearance and crispy feel as a mould. The 

 "curl" in the leaves of Peach trees, often so fatal in 

 the spring, he attributes directly to the attack of 

 another species of fungus, discovered and called by 

 him Spcerotheca Persica. This also invades the 

 Peach fruit some seasons, causing.rot of the crop. 



In the same rich, peaty, boggy localities, where 

 these several species of malarious cryptogams origi- 

 nate, is also found growing, with equal or greater 

 luxuriance, according to Prof. S., another species of 

 malarious fungus known as the Palmellce, or ague 

 palmellae, of algoid characteristics, whose poisonous 

 spores or miasm, elevated in nightly fogs and va- 

 pors, and inhaled by man, produce, as Prof. S. has 

 demonstrated, the common disease fever and ague, 

 and the other intermittent and remittent fevers of 

 kindred type. 



Sulphur is an agent known to control fungoid or 

 mucedinous growths of all kinds ; hence. Prof. Sal- 



