187^.] 



AND HORTlCULrURlST. 



183 



broad chisel cups in the body of the tree, from 

 the root up as hiah as you can reach. Do this 

 in the spring, and in a short time the cups will be 

 filled with the crude gum, which should be re- 

 moved before becoming too hard. The gum 

 should then be phiced in a small iron or earthen 

 vessel, and this be put in a larger one containing 

 water, which must be raised to the boiling point. 



frequently stirring the gum in the m^^antime. 

 In about an hour's lime remove from the fire 

 and strain the liquid through a coarse cloth to 

 remove the sediment and impurities. Spread it 

 thinly over the bottom of, plates or dishes to cool 

 and harden, after which it may be easily removed, 



J and can hardly be detected from the gum of 



i Arabia. 



Natural History and Science. 



COMMUNICA TIONS. 



THE SECULAR CHANCE OF VEGETATION. 



BY MR. MARC, BUDA-PESTH, HUNGARY. 



The periodical change of vegetation has often 

 been discussed, and its process has been confirmed 

 in every country. Thus Grisebach in his classical 

 work "• die Vegetation der Erde^'' relates the fact 

 that in the valleys of Guiana a .secular change 

 has taken place between woods and grass. This 

 is not an isolated fact ; on the contrary, many 

 more are extant, and of the most patent ones I 

 shall here put down a few. 



In the lowest strata of the moor and peat 

 lands of Jutland, that much split-up tongue of 

 land, in AVestern Europe, trunks of pine trees, 

 Fie a excelsa, Lamb, have been found, proof of 

 former existence of pine woods. That tree not 

 only is nowhere to be found any more in Jut- 

 land, but not even tradition hands down any 

 knowledge of its former existence there. On the 

 top of this layer of pine trees, trunks of the 

 German oak are found. There are but few isolated 

 trees of that oak found in Jutland nowadays. 

 The present woods are mostly Beech. 



Another free that has disappeared is Piceafuc- 

 c'nt/ero, Rick; there must have been once vast for- 

 ests of it on the eastern shores of the Baltic, and 

 in some sections of Southern France. Its prec- 

 ious petritied rosin is our present amber. 



The same process is now going on in New 

 Zealand with the Kauri fir, Dammnra Austrnlis, 

 Lamb., it disappears and, spite of pains and trou- 

 ble taken, will not succeed any more when 

 planted. In places where that tree does not 

 exist any more for a long lime, clumps are found 

 of its rosin, in a more or less hardened state. 

 Wherever that fir disappeared, there appeared 

 Pteris esculenta, the roots of which serve the 

 Maoris as food. A poor substitute for the valua- 

 ble ship-timber of the Kauri fir. 



Another evidence of the law of vegetable 

 change is the quick lu'climatization and aston- 



ishing spread of plants which have migrated into 

 distant countries. This is the case, notably 

 with Cynara scolymus, Linn., or artichoke, the 

 seed of which is easily transmitted by the wind 

 or by adhering to the coats of animals. Thus, 

 it was carried to the pampas of La Pl<\la by 

 a donkey, about the year 1769. Much to 

 the chagrin of the Gauchos, and to the disad- 

 vantage of their cattle industry, this plant 

 now covers very many squai'C miles. It 

 seems, in fact, to have found there a most 

 favorable soil, for its dimensions and devel- 

 opment may be called gigantic when com- 

 pared with its native ones. The traveler through 

 such districts of the Pampas must not leave the 

 narrow-trodden paths; if he does, he will be 

 lost amongst the dense and growing artichokes. 



Erigeron Canadensis has been imported into 

 England in the body of a bird ; has from there 

 spread all over Europe, and is now one of the 

 most troublesome weeds, found everywhere, 

 even on roofs and old walls. 



Xanthium strumarium, Linn., and ^T. eehina- 

 turn, Murr, came from the lower Danube, by 

 droves of pigs, into Hungary, and now troubles 

 all pastures as far as Northern Germaiiy. 



That water pest, Etodea Canadensis, Mich., has 

 multiplied enormously in the waters of England, 

 Scotland, Belgium, Holland and Germany, often 

 stopping up entirely drainpipes, and, in canals, 

 driving before it all other vegetation. 



The "Bulletin de la migration des vegetaux" 

 make mention of Lindernia pyxid(eria, Linn., a 

 scrophulancB, as having covered toward the end 

 of the last century the waters of the Scvre, near 

 Nantes, where that river joins Ihe Loire. It is 

 five years ago that a botanist of Nantes found to 

 his surprise that this Lindeniia was driven out by 

 an American llysanthes. M. lledatcs found in 

 186'), a groat many of these llysanthes, on the 

 slimy shores of Mayenne, and amon2;Ft them 

 choked the native Lindernia. 



On the other hand, how many migrations of 



