850 



THE YOUNG NATURALIST. 



irregularly lobed a second time, and sharply 

 toothed. This variety is always barren, and 

 persistent in ordinary- winters. 

 Poly. vulg". var. Semilacerum (Irish 



Polypody) is another elegant variety, in 

 which the lower half of the fronds are lobed 

 a second time, and the upper half are fertile, 

 and once lobed only. 



Poly. PhegfOpteris (Beech Fern) has a 

 slender, creeping, and scaly stem. The frond 

 is from six to twelve inches long, which is 

 pale green and hairy. The stipes is gener- 

 ally twice as long as the leafy portion. 

 The frond is triangular in form, and the 

 pinna? usually stand opposite each other in 

 pairs, the lowest pair being directed down- 

 wards, towards the root ; the upper pinnae are 

 united at the bases. Sori are found ©n the 

 venules near the base of the lobes. Fronds 

 appear in May. Found in damp woods, Sec, 

 and is local in its distribution. 



Poly. Dryopteris (Oak Fern). This 

 delicate little fern grows with a slender 

 creeping stem, and forms dense tufts. It 

 grows from six to twelve inches high, is of a 

 bright light green color, and quite smooth. 

 The stipes is twice as long as the leafy por- 

 tion, is slender and dark-colored. The frond 

 is divided into three branches, each triangular 

 in shape, and are so divided that each branch 

 is pinnate at the base, and pinnatifid towards 

 its point. Sori are dorsal, and very un- 

 equally produced in different localities. 

 Fronds appear in April. Found in moun- 

 tainous situations, and the dry part of damp 

 woods. 



Poly. Calcareum (Limestone Poly- 

 pody). This plant is very similar to the last 

 named, and is considered by some as a 

 variety only. It is distinguished (from P. 

 Dryopteris) by having its fronds less decidedly 

 three-branched, and its surface covered with 

 small glands, which give a mealy appearance 

 to every part, and may be seen by the aid of 

 a magnifying glass. The fronds are a dull 

 deep green, and the pinnse of the young fronds 

 are rolled up separately, instead of being 



; rolled up in three little balls. Sori are pro- 

 \ duced (in a marginal series) as the end of the 

 ( veinlets. Found in chalky soils. Rare and 

 J local. 



Poly. Alpinum (Alpine Polybody). 

 I This fern is the connecting link between the 

 ! Polypodies ( Polvpodium J and the Lady ferns 

 | (Athyrium). It has a short decumbent root- 

 stock, producing fronds in tufts from the 

 crown. The fronds grow from six inch to 

 three feet high, and are broadly lance-shaped, 

 with a short stipes, and scales. The pinna? 

 | are linear-lanceolate, and the pinnules ovate- 

 \ oblong with sharp coarse teeth. Sori form a 

 I series on each side of the midvein. Fronds 

 appear in May. Found in mountainous dis- 

 tricts in Scotland. 



(To be continued.) 



CONCHOLOGY. 



LAND AND FRESH-WATER SHELLS. 

 By H. T. Robson, Stockton-on-Tees. 

 (Continued from page 311 .) 

 FAMILY, LYMN/EACEA. 

 Genus, Planorbis. 

 The genera and species now to be described 

 are those which are fitted to live either on 

 land or in water, and can thus survive when 

 the pond or stream where they have been 

 living becomes dried up; thus although water 

 is their proper element, they may often be 

 found in great abundance in the beds of 

 streams and ponds which have recently 

 become dry for want of rain ; they are without 

 an operculum. In the genus Planorbis the 

 shells are coiled into a flat disc, very much 

 like an Ammonite, the size of the whorls in- 

 creasing slowly. The animal is small, with a 

 pair of long slender tentacles on the inner 

 side. The species are Comens, A Urns, Glaber, 

 Crista, Carinatus, Complanatus, Vortex, Sp.'rorbis, 

 Contortus, Fontanus, and Nitidus. 



Cornells. — This is by very much the 

 largest of the genus, a full-grown shell 



