52 

 The most uumerous geiieni areas follows : 



Specifs. Species. 



iSolanuiu 915 Pliyllauthus 447 



Euphorbia 751 j Erica 429 



Senecio GOl | Salvia.. 410 



Croton 461 I Peperoiiiia 389 



PoruLUS MONiLiFEEA AS A SHADE TREE. — M. Vail Hulle, curator of 

 the Eoyal Botanic Gardens at Ghent, writes as follows: 



Many kinds of trees, chosen for planting avenues, public promenades, »S:c., either do 

 not acconiiuodate themselves to all kinds of soils, or else require an inconvenient length 

 of time to attain to such size and development of foliage as will aft'ord the desired shade. 

 In consequence of this, the Canada poplar {I'opiilus Canadenslis) bas been largely planted 

 about Munich and other places in Germany. This tree grows quicklj^, and in almost 

 any kind of soil. Its only defect, as a shading tree, is that it sometimes, if left to itself, 

 shoots up into too spiral a form to be of service in that way. This, however, is easily 

 guarded against by heading dowu the young trees to the height of from 12 to 15 feet, 

 and paying some attention to the pruningof the branches for some time, so as to secure 

 the lorniatii>n of handsome crowns. Treated in this way, the trees are quite as effect- 

 ive at some distance as well-growu specimens of horse-chestnuts. — The Garden. 



The Fopuhifi C/cnadensis mentioned above probably means our cotton- 

 wood, ( PopuJus moiiilifera A it., of which F. Canadensis is a synonym.) We 

 wonld suppose the rapid us balsam l/era to be at least equally valuable 

 for the purpose of shade. 



Early FLOWERiNCr of the jasmine. — In consequence of the mild- 

 ness of the winter thus far, Jasminium nudrftonim, a Japan species of 

 jessamine in cultivation here in the open air, has been in flower since 

 near the 1st of January, two or three weeks, at least earlier than usual. 



MICIIOSCOPIG INVESTIGATIONS. 



Bv Thomas Taylor, MiciioscoPisr. 



Black-knot. — Entomologists and botanists are now pretty gener- 

 ally agreed that the black-knot of cherry and i»lum-trees is produced by 

 a fungus, but they have failed" thus far to defiue its internal structure. 

 Schweiuitz, the American botanist, who died in 1834, seems to have 

 been the first who suggested that it might be of fungoid origin, and he 

 named it ^Siyhwria morhosa. During the present year several correspond- 

 ents engaged in fruit growing have sent to the Department specimens 

 of cherry and plum tree black-knot, asking for information in relation 

 to its cause and cure. 



Hon. Marshall P. Wilder, of Boston, forwarded some specimens of 

 the black-knot on cherry-tree branches, which I used as the basis of 

 my experiments. The usual methods of investigating the black-knot by 

 Ijl'acing opaque sections of it under the microscope, gave results so un- 

 satisfactory that I determined to employ my usual methods of rendering 

 organic bodies transparent and yielding, by means of acids and alkalies. 

 In this way the higher powers of the microscope may be brought to bear 

 effectively on the fungus, its mycelium and S[)ores, if present. The im- 

 mediate use of strong mineral acids and caustic alkalies on suspected 

 fungoid bodies has this advantage, that these prevent the possibility of 

 theproduction of fungus growths by fermentation during the investiga- 

 tion. Portions of the black-knot were subjected to strong nitric acid 

 during several days, and then examined under low and high powers of 

 the microscope. Portions were also well washed in pure water, to free 

 them from acid, and then submitted to the action of caustic potash. 

 For the purpose of distinguishing colorless spores, mycelium, starch, 

 chlorophyl, and cellulose from one another, a solution of iodine, coa- 



