WINDSOR : THLASPI ALPESTRE. 



109 



Both, forms of Thlaspi, Mr. J. G. Baker informs me, are found in Tees- 

 dale, from which, locality he has kindly exchanged specimens with me. I 

 am thus enabled to compare recently collected plants from different places of 

 growth, and to judge, in some degree at least, how far they are essentially 

 j distinct, or owe their somewhat different aspects to adventitious circum- 

 stances, as the nature of the soil, altitude, exposure, &c. 

 j At Matlock, where I found it abundantly, the plant was growing in a 

 I sheltered situation, and attained a stature not generally equalled by that 

 I growing on Malham moor, in a more bleak and unsheltered part. There 

 appears to be a nearly similar difference of size in the two forms from 

 Teesdale. How far the difference of locality may operate in modifying their 

 growth and appearance it would be difficult to say, but I think it is not 

 unreasonable to admit its influence. I have a specimen of the Malham plant 

 grown in a garden, which is as tall as the Matlock one, and undoubtedly its 

 : size varies considerably in all its localities. 



To the supposed differences between the three forms named respectively 

 Thlaspi alpestre, T. occitanicum and T. virens, I have adverted in my previous 

 communications, and from more recent examination and comparison I have 

 little to add now. The fruit bearing race7ne, is ultimately elongate in all of 

 them, and of an oblong form. The silicle or pouch, varies from oblong 

 ! obovate to triangular-obcordate in all of them, but the former perhaps pre- 

 dominates in the Teesdale and Matlock T. alpestre, the latter in the Malham 

 I (and Teesdale), so called, T. occitanicum, the pouch in the latter and the in- 

 I tervening notch being also often a little wider, and the interlobular ridge, 

 | (an extension of the pedicel) more distinct ; this is sometimes equally apparent 

 I in both forms. The style is of about the same length in all. The size and colour 

 f of the petals is I think the same in all. The root-leaves are obovate, or sub- 

 j spathulate in both and attenuated into the petiole. The stem-leaves in both are 

 sessile and obcordate. The ISTamur plant seems an intermediate form between 

 the Teesdale or Matlock alpestre, and the Malham &c. occitanicum. It 

 has the stature and I think glaucescence of the former, with the somewhat 

 larger fruit of the latter. Does not this make it probable that the slight 

 differences between them are, in a considerable degree, if not entirely, the 

 result of contingent circumstances. I would however remark that the 

 glaucous hue of the foliage is as striking in the Matlock plant, as is its 

 i absence in the Malham or Settle form. If the latter be also found at 

 i Matlock, it escaped me this year, but as both forms grow in Teesdale, it is 

 possible the same may also occur at the former place. Upon the whole I 



