HARDWICKE'S SCIENCE-GOSSIP. 



203 



One of the Paludina vivipara was the largest I ever 

 took, and didn't my eyes glisten when I saw the giant 

 crawling up the muddy sides of the stream ; it was a 

 well-marked specimen with a longitudinal measure- 

 ment of 38-5 mill, and a transverse diameter of 

 the aperture of 19 mill. Bythinia tentaculata was 

 there in plenty. 



Valvata piscinalis was in tolerable abundance in the 

 weeds on the bottom of the river, and also some 

 little specimens which closely simulate it on first 

 look, and of which I must warn the young collector, 

 viz. baby/ 1 , vivipara; but by an old hand they can be 

 at once distinguished, for where is the umbilicus, the 

 peculiar twist on the last whorl as you look at it 

 from the side of the aperture, and the old oper- 

 culum ? Valvata piscinalis is umbilicated very 

 distinctly, the operculum looks old and brownish, and 

 it has a peculiar twist on its last whorl ; the young 

 P. vivipara has no, or if present, it is'extremely slightly 

 marked, umbilicus, the operculum is so thin that it can 

 scarcely be distinguished on the body of the animal, 

 and there is none of that peculiar twist on the last 

 whorl. The young P. vivipara with the animals in 

 them look very pretty things indeed, and they would 

 make very pretty things too for the collection, 

 because they appear to be marked with three black 

 bands which come out well in relief; but on extracting 

 the animal only a transparent horn-coloured and ex- 

 tremely fragile shell is left without the banding, for 

 that has disappeared with the animal, it being present 

 on that portion of the animal which is known as the 

 mantle. As the shell becomes older, this colour is 

 laid down in it by the free edge of the mantle from 

 which it is secreted, and thus the characteristic 

 markings of the adult shell is typified in the markings 

 on the mantle of the embryo. 



Several purple-mouthed Limtuza palustris were also 

 taken, and plenty of Limnaea peregra and Limnaa 

 auricularia with "intermediate forms" between 

 these last two species. Limnma peregra, vars. 

 labiosa and succinevformis, were the most plentiful, and 

 some specimens which cannot be told whether they 

 are peregras or auricularias, and which is best to 

 designate as " intermediate forms " for Limnaa 

 auricularia seems to have been evolved from Limncea 

 peregra, not only because of the presence of these 

 " intermediate forms," or mesostates, as they may be 

 termed, but on account of the great resemblance the 

 two species bear to one another in their internal 

 structure, especially in the reproductive organs, where, 

 if anywhere, the greatest differentiation would be 

 expected. All the Limnsea have been seen floating ; 

 Mr. Wallis Kew first observed Z. truncatula doing 

 this in Lincolnshire ; and I have lately had the 

 pleasure of completing the list by observing L. 

 auricularia doing the like. 



The pretty and delicately formed Physa fontinalis 

 was also taken ; and also specimens of a small narrow 

 and thin Z. stagnalis which to me does not seem 



worth a variety-name, but which nevertheless is 

 named var. fragilis. There must indeed be some 

 hard and fast line drawn in naming varieties, or else 

 we shall all be overwhelmed in a deluge of variety- 

 names, for in no other zoological group, with the 

 exception, perhaps, of the leeches, does variation 

 occur to such a great extent as in the Mollusca. 



AFTERGROWTHS AMONG HARDWOOD 

 AND CONIFEROUS TREE STUMPS. 



By Robert Coupar. 



THE aftergrowth of Hardwood and Coniferous 

 tree stumps is a subject of much interest to 

 the scientific and practical student, inasmuch as it 

 affords us a pleasing and instructive study to master 

 the details and explain the cause of this curious and 

 interesting freak of nature. 



That some trees of the hardwood species do grow 

 after being cut down is well known ; the roots draw 

 sap from the soil which circulates through the root 

 and stimulates those latent and hidden buds contained 

 in the bark into growth, becoming shoots, and finally 

 increasing to copse, ultimately reaching a tree none 

 the less inferior to its parent, which may be again 

 cut down and the same process repeated over and 

 over again. 



Now, if we were to destroy the bark, this physio- 

 logical property would be entirely destroyed, hence, 

 in regenerating copse woods, the great care of pro- 

 tecting and saving from injury is apparent. 



Now, in the case of coniferous trees which have 

 not this physiological property of pushing out young 

 shoots and leaves from the felled stumps, how can 

 they grow as formerly, is the main inquiry ? 



In some works, for instance, arboricultural work, the 

 authors have fallen into the error of saying they have 

 the power of growing after being cut down : and 

 recently, at a society's meeting at Edinburgh, some 

 authors positively asserted they had known several 

 instances of isolated and other stumps continue growing 

 for very many years]after being cut down. Such asser- 

 tions are entirely misleading, and have been given 

 before the writers made themselves in the least ac- 

 quainted with thelife and various functions of plant-life. 

 We have observed that hardwoods produce leaves 

 and shoots which elaborate, the sap returning again 

 by the bark to be converted into woody tissue, hence, 

 no leaves, no growth, unless by a system inarching or 

 engrafting. 



Since, then, conifers are not capable of sending out 

 shoots and leaves, they have no elaborating organs 

 of their own ; in other words, they have no lungs, 

 for the leaves are compared to the lungs ; they are 

 the breathing organs of the plant. Then these coni- 

 ferous stumps cannot possibly grow after being cut 

 down, unless they have been previously engrafted 



