12 ROCHESTER ACADEMY OF SCIENCE. [Oct. 8, 



IXTROUUCTIOX OF SpECIES. 



The number of introduced plants increases every year. In the 

 Flora of the State of New York, published in 1843, the number of 

 introduced plants for the whole State is given as 160. The number 

 in this list is 263, of which seven are indigenous to the State, though 

 they are introductions to Monroe county. Several of these newly 

 introduced plants come from the West, and it has been noted that 

 species new to this district are frequently found along railroad tracks 

 and in lumber yards. Some species have increased so rapidly that 

 they have already become a nuisance, and others threaten to become 

 so. Among the former may be particularly mentioned Chrysaiithemum 

 Leuca?it/iemian, Daucus caroia, and P/a/itago lanceohita. Arelilotus offici- 

 nalis and AT. alba, which a few years ago were but rarely seen are 

 becoming very plentiful along the roadsides and in waste places. 

 Hieracium aurantiacum has been reported in but few localities thus 

 far, but where it has become established it has multiplied with great 

 rapidity. Lactuca Scariola was first noticed only a few years since, 

 but is now very frequent and in some places abundant. Cichoriurn 

 Iniybus is a common weed. Cenchnis iribiiloidcs is rapidly spreading 

 eastward along the Central railroad. Trifolium hybridum is becoming 

 quite as common in fields and along roadsides as T. repens. 



As Rochester has been for many years a center of the " nursery 

 business", the frequent occurrence of exotic shrubs and trees through- 

 out the city and its suburbs is a natural result. In the case of nurseries 

 which have been abandoned on account of the growth of the city, 

 these foreign trees and shrubs are sometimes left to grow as if spon- 

 taneously. In many such cases it is difficult to draw the line between 

 plants which should or should not be included in the list. For 

 example, in abandoned nursery grounds on North Union, Prince and 

 Augusta streets the following trees and shrubs are now growing : 

 Tilia Europcea, Querais Robur, Casianea saliva, J^(?gus sylvalica, Salix 

 Caprea, Populus dilalata, and Juuiperus Virgifiiava var. prostrata. 

 Where these plants seem to have become so firmly established that 

 they would doubtless propagate if undisturbed, they have been num- 

 bered in the list. 



Disappearance of Species. 



Pingicicida vulgaris, reported by Dr. Chester Dewey and Dr. C. M. 

 Booth as growing on the rocks near the Genesee Falls, is extinct. 



