23 



perfectly green, even far advanced into the next season, and 

 under glass are green for three years. I have now in my 

 possession pinnae of three years' growth, picked from the 

 same plant at the same time. 



7th Column. — The differences here are as much the 

 same as in Column 3 ; but, as treating of the fronds them- 

 selves, and not of the parts, are of marked importance, 

 and may be taken under ordinary circumstances as a good 

 diagnostic. 



8th Column. — The three forms are here taken when 

 they have felt the effects of a severe frost, and you will 

 observe that Lastrea propinqua, which is sub- Alpine (and 

 if it were only a variety of Lastrea filix mas, would on 

 that account be more hardy), is perfectly deciduous and 

 perished. This surely is very strong confirmation in 

 favour of its being a true species. Lastrea filix mas is 

 prostrate in winter, but not deciduous, and Lastrea 

 pseudo mas is evergreen or sub-evergreen, and preserves 

 its erect position throughout, unless, as before stated, 

 beaten down by snow. 



9th Column. — We have here a good characteristic for 

 one out of the three forms. In Lastrea propinqua and 

 Lastrea pseudo mas the indusia embrace the spore cases, 

 and are persistent and entire, and in Lastrea filix mas 

 the indusium (taken when quite young) in section, exactly 

 resembles an inverted soup plate, and is eventually 

 evanescent. 



10th Column. — This, the most knotty point, viz. the 

 possibility of distinguishing each by the markings of its 

 spores, is a most difficult question to decide, there being 

 such an infinite variety of causes, which militate against 

 accuracy of manipulation, etc. I will enumerate a few. 

 The difficulty of procuring the spores of each form of the 

 same age and of the proper maturity, their extreme 

 minuteness (viz. about the 1,400th of an inch in length), 

 and their comparative thickness and opacity, which when 



