Wednesday, September 01, 2010

corydalis / valley heights of Yorkshire

The rather faded notice at the base of Hambleton Hough in Yorkshire tells us that the flora of this mountain includes "Climbing White Fumitory". Once you have ascended the 35 meters from here to the summit (we used GPS to check this) you'll find the plant in most seasons - Climbing Corydalis, (Ceratocapnos claviculata, formerly Corydalis claviculata). The name "White Climbing Fumitory" is not found in McClintock and Fitter nor in any flora since, but it still clings on from the botanical past. It isn't a good name, though. The fruit of Fumitory is an achene, while Corydalis fruit is a capsule.

Achene - a dry, 1-seeded, indehiscent fruit.
Capsule - a dry, many-seeded, dehiscent fruit.

They never explain this stuff in the wild flower books, but I suppose the logic is this: if a fruit contains more than one seed, then it needs to scatter them to prevent them all germinating in the same place. Therefore some sort of process of breaking open (dehiscence) and scattering of the seed is more or less inevitable (there are a few exceptions). On the other hand, if there's only a single seed, then it might as well hang on to its protective fruit-coat until germination.

(Several attempts to use supermacro in a dark wood at sunset - not a good combination...)

John Durkin writes, on the BSBI site:

"In County Durham it could almost be said to be an indicator of PAWS woodlands (plantations on ancient woodland sites), being often abundant under conifers on ancient woodland sites, but very scarce in broadleaved ancient semi-natural woodland and almost unknown in recent plantations. PAWS woodlands on slightly acidic glacial sands have the best populations."

That describes Hambleton Hough perfectly, where the natural woodland was cut down by a former owner and replaced by Scots Pines. The ground flora is bracken and very little else, and yes, it is a glacial deposit left behind by the Humber glacier in the otherwise dead-flat part of the Vale of York. Well, apart from its neighbouring twin peak, Brayton Barf, which also has plenty of C. claviculata.

Hambleton Hough and Brayton Barf are accumulated heaps of glacial debris that built up around an original nub of Bunter Sandstone (Triassic). The debris is mainly coarse sand of a reddish cast. I like to imagine that this sand was scoured off North Yorkshire sandstone cliffs like those still to be seen at Sutton Bank, but this may be wrong.



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