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Notes - Damage to the Northern Pennines I Wet May and Poa trivialis I Pores for thought 9ReferencesCORNER, R.W.M. 2004. Carex vaginata Tausch(Cyperaceae): a sedge new to England. Watsonia25: l27·l30.CORNER, R.W.M., ROBERTS, F.J. & ROBINS ON, L.2006. Sheathed Sedge Carex vaginata: an updateon its status in the Northern Pennines. BSBI News101: 6·8.RATCLIFFE, D.A. 2002. Lakeland: The Wildlife 0/Cumbria. New Naturalist, HarperCollins, London.ROBERTS, F.J. 2002. After Foot and Mouth, CrossFell in bloom. Carlisle Naturalist 10(2): 33-43.ROBERTS, FJ. 2003. Cross Fell update, 2003. CarlisleNaturalist 11(2): 47·52.ROBERTS, F.J. 2004. A further note on the flora of theCross Fell range. Carlisle Naturalist 12(2): 52·56.ROBERTS, F.J. 2005. Further notes on the flora of theCross Fell range. Carlisle Naturalist 13(2): 20·24.ROBERTS, F.J. 2005. Water Sedge Carex aquatilisWahlenb. in a montane mire site. Carlisle Natural·ist 13(2): 15·18.ROBINS ON, L.M. 2003. Observations on Alopecurusborealis at Green Fell in the Northern Pennines,Cumbria, after Foot and Mouth. BSBI News 93:11·12.STOTT, M., CALLION, J., KINLEY, 1., RAVEN, C. &ROBERTS, FJ. 2002. The Breeding Birds a/Cum·bria - A tetrad atlas 1997-2001. Cumbria BirdClub.A wet May and Poa trivialisEDWARD PRATT, 7 Bay Close, Swanage, Dorset, BH19 IREFive Floras in my possession give the maximumheight of Poa trivialis (Rough Meadow·grass)as respectively 60, 60, 90, 90, or 100cm. Thisyear, with May being very wet, several arounda manured climbing rose in our garden reachedwell over 100cm. The tallest reached 169cm... , Yes, I do not do much weeding!Pores for thought: Can you separate Convolvulus and Calystegiavegetatively?JOHN POLAND, 91 Ethelburt Avenue, Southampton, Hants., S016 3DF. jppI97@alumni.soton.ac.ukNon-flowering bindweeds can easily beconfused in the field, particularly when record·ing atypical or poor specimens. Thankfully, thepresence and arrangement of stomata can helpclinch identification. Stomata (singular stoma)are pores on the leaf surface used for respirationduring photosynthesis. The actual opening maybe closed to prevent dehydration but this makesno difference to our field observations.Contrary to popular belief, stomata are indeed afield character - not just a microscopic one -and can normally easily be seen as little whitedots under a hand lens (best x20). It is primarilythe larger sized pair of guard cells that surroundthe pore that we actually see.The majority of our vascular flora is amphistomous(stomata present on both sides of theleaf, although often in unequal proportions) orhypostomous (stomata on the lower (abaxial)side of the leaves only). Epistomous species(those with stomata on the upper (adaxial) sideof the leaves only) are generally rare althoughsome grasses, and aquatic plants with floatingleaves, qualify in this category (totallysubmerged aquatic plants do not developstomata since they would effectively drown).As a general rule, stomata are arranged in paral·lellines in monocots (many exceptions!) and arerandomly scattered in dicots.The presence of stomata below is generallylittle use for identification (except for theirabsence in grasses) and the structure of thecuticle can make them appear obscure or absent.It is thus the presence, or absence, of stomataabove that is the useful character. A classicexample is Carex since there are only 6 speciesin the British flora with stomata on the upperleaf surface (try and find them all - C. curta,C. nigra, C. aquatilis, C. rostrata, C. recta andC. salina).There are many examples where stomataprovide the best vegetative character. Forexample, the leaves of Thymus polytrichus(Wild Thyme) have stomata on the uppersurface, most unlike the remarkably similarleaves of Thymus pulegioides (Large Thyme) inwhich they are absent.Calystegia and Convolvulus provide a perfectexample of how examination of stomata can beutilised in identification. Convolvulus arvensis(Field Bindweed) has stomata scattered all overthe upper surface of each leaf, whilst Calystegiasepium (Hedge Bindweed) and C. silvatica(Large Bindweed) have the stomata confinedabove to just the margins of the larger veins.C. pulchra (Hairy Bindweed) has stomataabsent above (petiole or stem hairs alone are not