THE FLORA OF HALIFAX. 239 



becoming acquainted with the various processes of life." In 

 comparison with other plants, their systematic study is 

 difficult. Some of them cannot be preserved at all — thev 

 putresce ; and those that do dry, so shrivel up in the process, 

 that little of their original character remains. Careful draw- 

 ing is the best means of dealing with them for systematic 

 purposes. Another difficulty is. that we are never sure of 

 seeing a second time those that we may want. Some certainly 

 reappear, year after year, in the same place, or under similar 

 conditions in fresh places, and one can always rely upon find- 

 ing them at the proper time, if needed. Others are very 

 inconstant in their appearance : they may be found once and 

 not again, perhaps for years, if at all. Scores we never have 

 seen but once, although many of them have been carefully and 

 repeatedly sought for in the same and similar places. This 

 applies to macro- and micro-species alike. Two instances may 

 be given. Pocillum Needhami was found by Mr. J. T. Aspin 

 and myself on fallen oak-leaves in Elland Park Wood, in 

 1S94, and proved to be a new species. All the specimens, 

 after drawings and descriptions had been taken, were sent to 

 Kew. More were sought for. The place has been visited times 

 out of number, year after year, and thousands of dead oak- 

 leaves carefully examined, all to no purpose ; no trace of it has 

 since been found either there or anywhere else. Two speci- 

 mens only of another very distinct new species, Lactarius 

 glaucescens, were found in Wade Wood, Luddenden Dean, in 

 1S99, and one in North Dean Wood the year following, but 

 all search for more has been in vain. Half these specimens 

 are at Kew, and half at the British Museum (Natural History). 



There is another peculiarity to note in connection with 

 fungi. Species occasionally appear in vast abundance in a 

 place for one, two, or three years in succession, then totallv 

 disappear, and are seen no more for years, if ever, at that 

 place. Desmazievella acicola, a most beautiful saucer-shaped 

 fungus, which grows only on dead pine-needles, was found by 

 Mr. Needham in hundreds in Crimsworth Dean in 1897. 

 They vanished the same year and have not since reappeared. 

 Fungi seem to have periods of virulence in one locality and 

 then die out, or move on to fresh fields of action. 



Numerous unknown species, of which only two or three 

 specimens were discovered, are laid on one side, along with 

 such drawings and descriptions as could be taken at the time, 



