172 



Mason : Nightingale at Lincoln. 



The chang-es incident to tillage operations often bring- about 

 changes of flora ; but, as arable land is rare in the Halifax 

 parish, this factor is unimportant here. Corn-field weeds, and 

 even h£dge-row plants, such as the Poppy and the Crosswort r 

 are quite rare in Halifax. As in most suburban districts, arable 

 land has diminished rather than increased since Bolton's time, 

 which cause accounts for the comparative disappearance of 

 some plants common in his time, such as Crosswort. 



Among natural agencies, physiographic factors, such as land- 

 slips and floods, may have been operative to some extent; but 

 all the evidence in my possession is against such causes being 

 responsible for the introduction of fresh types; though I regard it 

 as more than probable that in a few cases plants, e.g., Pyrola, may 

 have been exterminated from particular stations by such agencies. 



Then, again, birds are no doubt responsible for carrying 

 seeds from one locality to another ; but when, as .is now of 

 course usually the case, the seeds drop in places occupied by 

 other adult plants it is not often that the seedlings of such 

 plants will be able to oust adult and robust species. For 

 example, although the spring Bluebell produces ripe seed in 

 abundance, I have noticed that it is only in places unoccupied by 

 other plants that the seedlings usually develop into adults. It 

 is quite possible, however, that a few plants, of which I may 

 mention Geranium sylvaticum, have been recently introduced 

 into the Halifax district by this means. 



My study of Halifax plants, then,' has brought me to the 

 conclusion that apart from obviously artificial causes, the changes 

 observable in the flora of this area during the last century and 

 a quarter are well-nigh negligible. This is so in regard to the 

 introduction of new species, in regard to the extinction of estab- 

 lished species, and even in regard to the change of habitat of 

 such plants. Mr. F. A. Lees states* that ' the natural stay 

 of species may be long or short,' but until the author of 'The 

 Flora of West Yorkshire' gives positive evidence of a 'natural 

 short stay ' of some plants, I must regard such a phenomenon 

 as highly exceptional. 



NOTE— ORNITHOLOGY. 



Nightingale at Lincoln. — A Nig-htingale (Daulias luscinia L., $) has 

 taken up his abode in the Arboretum here, and on Friday, the i rth May, 

 I both saw and heard him. — J. Eardley Mason, 27, Cheviot Street, 

 Lincoln, 13th May 1900. 



* 'The Naturalist,' Feb. 1900. 



Naturalist, 



