162 



KNOWLEDGE, 



[July 1, 1898. 



of the leaves below. In the dead-nettle, centuary, pimpernel, 

 and several St. John's worts, this occurs. Grooved, fluted, 

 or ridged sterna are also characteristic of such plants as 

 the bedstraw, violet, ragwort, groundsel, knapweed, dock, 

 wild mustard, shepherd's purse, pennycress, horsetails, 

 umbelifers, and others ; and it is interesting to observe in 

 some of these how one cauline groove is made to serve a 

 number of leaves. In the laboratory it is often important, 

 when pouring a solution from one vessel into another, not 

 to lose a drop ; the chemist eflects the transference easily 

 by using a glass rod to guide the liquid. Grooved and 

 striate stems act in the same way. The rain sometimes 

 takes a spiral course, as in the sow-thistle. The stem of 



BRITISH 



Fig. 3. — Rain-condueting Cliaimels: 1, Dead Nettle; 2, Tetcli 

 Stem; 3, Bedstraiv; 4, Carex; 5, Pennycress; 6, Ligule of Grass; 

 7, Leaf-stalk of Cow-parsnip. 



this plant is round, smooth, and coated with wax. There 

 are no grooves, but each leaf on the stem is sessile and has 

 large auricles at its base, which shoot the water over on to 

 the leaf next below. Some splashing results from the 

 falling water — grooved stems are designed to avert this — 

 but in the sow-thistle there is little loss, for the large 

 leaves at the base of the plant form a capacious basin, in 

 which most of the spray is caught. The water is projected 

 in this instance upon the next lowest leaf, and, therefore, 

 in its descent follows the genetic spiral ; but the rain may 

 be thrown on a leaf more remote, and then there are 

 several spiral streams circulating round the stem. 



The foxglove and muUein have nodding leaves ; one 

 portion of the rain drains inwards, but as the upper part 

 of each leaf slopes outwards, some water flows to the apex 

 and drops down on one of the lower leaves, where it is 

 again deflected towards the stem. As the lowest leaves are 

 much larger than the others, the great proportion of rain 

 falling on the plant is ultimately collected in the vicinity 

 of the root, and the loss through splashint; is reduced to a 

 minimum. But it must not be assumed that this is the 

 end of all the grooves which occur on leaves and stems ; 

 many of the narrower furrows resist the entrance of water, 

 and are probably of use in preventing rain from gaining 

 access to the stomata. Furrows of this description are 

 found in a number of grasses. There are also some grasses 

 with an arrangement which prevents water lodging between 

 the sheathing petiole and the haulm or stem ; the ligule 

 acts as a kind of dam, which forces the water that flows 

 down from the leaf-blade to escape at the sides of the lamina 

 and descend on the outside of the sheathing petiole. On 

 the leaf-stalk of the Nile lily, whose white trumpet-shaped 

 spathes are familiar objects in florists' windows, there is a 

 similar contrivance. 



The absence of wax and a peculiar smoothness of surface 

 enables one easily to distinguish those channels which act 

 as rain conductors. They recall irresistibly the shallow 

 gutters of clay employed for the distribution of water, seen 

 in Egypt and other lands where from time immemorial 

 artificial u-rigation has been practised. 



a!«<@S> 



t^-^ 



ORNiTHOLOGIC/'tL 



" ^ N OTES 



Conducted by Harby F. 'Witherby, f.z.s., m.b.o.u. 



A British-taken She.vbwater identuied for Fobty-fi\te 

 Years as Pii/Hnus obxcurus, now found to be P. assimilis. 

 — In the 1880 edition of Mr. Howard Saunders's well- 

 known " Manual " will be found, under the heading of the 

 Dusky Shearwater {Pii/finus obscurus), a description of a 

 bird which was brought to Yarrell by ^Ir. B. Blackburn, 

 who said that it was caught on a small sloop off Valentia 

 Harbour, in County Kerry, on May 11th, 18-53. This 

 specimen was exhibited at a meeting of the Linnsean 

 Society. Another specimen was found dead in Suffolk 

 about April 10th, 18-58, and was exhibited by Mr. Osberfc 

 Salvin at a meeting of the Zoological Society. At a 

 meeting of the British Ornithologists' Club, held on 

 March 16th, 1898, Mr. Howard Saunders exhibited the 

 Valentia specimen, and remarked that " recent investiga- 

 tions by Mr. Ogilvie Grant in the islands near Madeira, as 

 well as Mr. Boyd Alexander in the Cape Verde Archi- 

 pelago, had aroused a suspicion that there might be an 

 error in the identification of the Irish specimen. The 

 authorities of the Science and Art Museum of Dublin, 

 having kindly forwarded the example in question, for com- 

 parison with the specimens of P. obscurus in the British 

 Museum, it is clearly established that this is not P. obscurus, 

 but the closely allied P. assimilis of Gould. This may be 

 distinguished from P. obscurus by its smaller size, by the 

 white or pale centres to the inner webs of the primaries, 

 the white under tail-coverts, and a more decided white line 

 on each side of the neck. The identification is confirmed 

 by Mr. Osbert Salvin. P. assimilh breeds in the islands 

 of the Madeira and the Canary groups, as well as in the 

 Cape Verde Islands, while P. obscurus breeds in the Ber- 

 mudas and the Antilles. Both species have a wide range." 



E.VRLY ArRH AL OF THE SwALLOW (//. rUStico). 1 SaW the 



first swallow this year on March 14th. This is to me a 

 record date for swallows, my previous earliest date being 

 March 2.5th. Perhaps the general mildness of the season 

 may account for this. Has anyone else seen one so early ? 

 — E. SiLLENCE, Church Street, Komsey. 



White Waqlail in Coirniy Mai/o (The Field. May 21st, 1898).— 

 Mr. Robert Warren reports that Mr. Kirkwood found a party of five 

 iif tlie*e birds on Bartragh Island, County Mayo, on April 30th, and 

 ii flock of fifteen on May 10th. Mr. Kirkwooi seeured in all six 

 specimens. Mofarilla alha has uow been recorded only six times for 

 Ireland, and it is a curious fact that five of these occurrences have 

 been on Bartragh Island, the other being on Achill Ishind. Further 

 search along the west coast of Ireland, which has been much neglected 

 by ornithologists, may result in establishing the White Wagtail as a 

 regular spring visitor to Ireland. 



All contributions to the column, either in the way of notes 

 or photoyraphs, should he forwarded to H-ABRY F. Witherby, 

 at 1, Eliot Place, Blackheath, Kent. 



Note.— The first issue of Knowlbdok containing British Ornitho- 

 logical Notes was that for October, 1897. 



