225 



altliouffh liitberto neglected agriculturally, may be fouud of value in 

 some situations. 



Another correspondent sends specimens of a grass whicli he says 

 grows freel}' on the poor land of a neighboring farmer. It is the Fes- 

 iuca ieneUa, which is notorious for its growth on dry, thin soils, and the 

 more of it a farmer has the poorer he will be. 



Mr. J. M. Morehead, Greensborough, North Carolina, writes to inquire 

 the botanical name of a grass found in a few places in that and adjoining 

 counties, where it is known by the name of mountain-grass. It is 

 the tall oat-grass, Arrhenatherum avenaceum, and is well known on 

 the continent of Europe as a valuable agricultural grass. Mr. Morehead 

 says it is "the earliest of all "our grasses, is admirably adapted to 

 X^asturing, withstands the freezes of winter and drought of summer well, 

 and it is almost impossible to kill it out by continual pasturing. With, 

 the exception of clover, it is the very best grass for this section of coun- 

 try. It yields annually two or three excellent crops of hay." 



MICROSCOPIC INVESTIGATION. 



PEAR-TEEB BLIGHT. 



By Thomas Taylok, Microscopist. * 



" For nearly a hundred years, blight of the pear has been a terror and 

 despair to growers of its fruit." This disease is known under a variety 

 of names — winter or frozen sap blight, leaf blight, summer blight, &c. 

 It is quite different from insect blight. Its true character is, doubtless, 

 of fungoid origin. Since the temperature and hygrometric state of the 

 atmosphere and the 'conditions of the soil, whether acid or alkaline, 

 l)ulverent or stili", aftect fungi by either retarding or fostering their 

 growth, it becomes a matter of iuterest to ascertain how far observa- 

 tions made in relation to pear-tree blight will agree with the fungus 

 theory. 



Some forms of fungus are favored by heat and dryness, such as the 

 oidium oi the European grape-vine, while the fungus of the native 

 grape-vine is favored in growth by moisture and heat. The lirst may 

 be called a saccharine and the second an acid fungus, being favored by 

 the acid condition of the leaf and wood. 



Yeast, which is a fungus of a low order, when in its active state 

 always exhibits an acid reaction ; if well washed, the globules become 

 much less active ; but by exposure for a few hours to the air their activ- 

 ity is restored, the acidity being thereby again developed. The addi- 

 tion of a small quantity of vegetable acids, such as acetic or tartaric, 

 to washed yeast immediately restores its activity, but when a larger 

 quantity of acid is employed the process of spore-budding is arrested. 

 The mineral acids, such as sulphuric, even in small quantities, immedi- 

 ately stop yeast fermentation ; sulphurous acid acts in like manner, 

 A small quantity of free alkali, or a strong solution of common salt, also 

 prevents its fermentation. Nitrate of silver, corrosive sablimate, and 

 sulphate or acetate of copper checks its growth immediately on appli- 

 cation ; also oxide of manganese, oxide of mercury, strychuia, small 

 quantities of kreosote, oil of turpencine, and mimy other essential oils. 

 When, however, the low forms of fungi once commence, the vegetable 



