October 31, 1872. ] 



JOUKNAL OP HORTICULTURE AND COTTAGE GARDENER 



349 



which have been very much diseased. I did not obtain above 

 half a load of good ones out of the whole crop. The ground is 

 nearly all clay, and in one part some ashes were dug in, and 

 I found that the Potatoes were almost free from disease. I 

 should like the opinion of some Potato-growers whether fine 

 ashes mixed in the clay would not improve the soil for Potato 

 culture. — D. Thornbee, Denton Rectory. 



NOTES AND GLEANINGS. 

 The Royal Horticultural Society's Shows next year will 

 be January 15th ; February 12th ; March 5th and 19th ; April 

 2nd and 16th ; May 7th, 21st, and 22nd ; June 4th, 5th, 6th, 

 and 18th ; July 2nd and 16th ; August 6th and 20th ; Septem- 

 ber 3rd and 17th ; October 1st ; November 5th ; December 

 3rd. 



Undee the popular name of Spanish Oystee Plant 



Messrs. Stuart & Mein, nurserymen, Kelso, have cultivated 

 largely the Scolymus hispanicus. In Spain the roots are 

 much used as a kitchen vegetable. They require to be boiled 

 two hours before they are thoroughly tender. They are deli- 

 cately flavoured. 



We notice that the Alexandra Palace Company adver- 

 tise Flower Shows to be held in May, June, and July, and an 

 International Pruit Show in August, 1873. Prom this we 

 may infer that the Alexandra Palace will be open to the public 

 in May next. 



The following is an extract from a letter we have 



received from the banks of the Tweed : — " You have no idea 

 what sort of weather we have been having ; at this moment 

 it continues to pour. Some corn is still out, and what is in 

 stack is in a pitiable state. Turnips are perished, and are 

 nothing but tops. Potatoes are not worth lifting, and the 

 prospect for the poor is anything but cheering. If the rain 

 do not cease no autumn Wheat will be sown." 



An American paper states that the old Elm tkee under 



which Washington took command of the armies of the United 

 States is still standing at Cambridge, Massachusetts, with an 

 iron railing around its ancient trunk, and a granite monument 

 beneath its branches, but is beginning to show the effects of 

 old age. Recently one of its largest branches, measuring up- 

 wards of 30 feet in length and a foot in diameter, fell to the 

 ground. The venerable tree will soon disappear with other 

 relics of the revolutionary period. 



SOME PREDATORY INSECTS OP OTJR 

 GARDENS.— No. 37. 



Befoee entering upon the main subject of this article, I may 

 allude with some measure of satisfaction to the complete 

 exoneration of the insect tribes from having any part in bring- 

 ing about or fostering the Potato disease, which is clearly 

 shown to be of a vegetable character. No doubt, various 

 species of insects appeal- upon the plant, or attack the tubers 

 independently, or in connection therewith, but in the case of 

 the particular sufferers by this malady, insects when they visit 

 them act rather as wholesome scavengers and destroyers of the 

 offensive and decaying. Worthington G. Smith, Esq., in his 

 interesting paper upon this disease, has, though only professing 

 to execute a compilation, brought out some new facts and set 

 old ones in a stronger light. 



The interesting account of the purple-leaved variety of the 

 Birch, which has recently been published, renewed the wish I 

 have long felt, that this tree were more largely used for orna- 

 mental purposes in our parks and pleasure gardens. It is 

 one of those trees which, for my own part, I cannot see 

 would be objectionable planted upon lawns or in suburban 

 gardens, where it would be in proximity to flower-beds, though 

 I am aware that many think differently, and oppose the in- 

 troduction of trees or shrubs of size amongst flowers. The 

 Birch is, however, so light and airy a tree, that its shadow could 

 hardly prove injurious to any plants beneath it, and the cul- 

 tivation of it is evidently progressing in the south, where 

 Loudon's objection to its admission into the ornamental 

 garden— namely, that it is too common in its wild growth, 

 does not apply, though valid enough as regards its cultivation 

 hi Scotland. To some persons who have seen it in its High- 

 land solitudes, its graceful form in the garden is a pleasing 

 reminder of days spent 



" Where weeps the Birch with silver bark, 

 And long dishevelled hair." 



The assertion that trees in or near a garden are apt to 

 transfer their insect habitants to shrubs or plants beneath 

 them, has some little weight, but I do not think it has much ap- 

 plication to this tree, though the Birch has many insect 

 enemies, some of which mar the appearance of the foliage, 

 while others attack the wood. Not all the knots or excrescences 

 which are to be seen upon the Birch are to be ascribed to the 

 punctures of insects, however, and I believe that the twig- 

 tufts (which have been compared to rooks' nests in miniature) 

 occasionally disfiguring the branches, are not tenanted by 

 insects, nor the results of then - visits. Such was the opinion 

 of Rennie, though a modern author with more knowledge of 

 botany than Rennie possessed, seems to think these abnormal 

 growths must be thus produced by some Cynips. As in other 

 cases where the Cynipidse are concerned, there is a difficulty 

 in ascertaining the habits of the species which has been at 

 work, or even of identifying it. On the trunk wens and ex- 

 crescences also appear, not all of which are caused by insects. 

 Some of these growths which have been produced through 

 an extravasation of the sap, are out of all proportion to the 

 insects that caused or inhabited them, and it is my opinion 

 that some irritative action is set up by the insect 's puncture 

 through the ejection of an acrid fluid into the wound, as in 

 the well-known instances of the wasp and bee. On the leaves 

 we may now and then find galls which are produced by an 

 insect of a different order to the gall flies proper, a dipterous 

 insect of the genus Cecidomyia. Minute two-winged flies are 

 developed from these, but I have not had an opportunity of 

 fully investigating them. 



Three species of saw-flies have been noticed which inhabit 

 the leaves of the Birch, and in some seasons these are so 

 numerous in the larval condition, that young trees from a 

 short distance off assume a whitish appearance. This may 

 occur in May, or in September and October. PhyUotoma 

 fuligmosa and. P. mellita form blotches upon the leaves, 

 which are not unlike those which are the habitations of small 

 moths of the genus Micropteryx. Of these saw-flies, P. rnellita 

 seems abundant near London, and its economy has been care- 

 fully described by Mr. Healey. The imagos or flies are out in 

 May and June, when, of course, the eggs are laid sometimes 

 only one on a leaf, at other times several ; as many as seven 

 have been noticed, more than a leaf will afford sufficient food 

 to, yet, according to observation, they seem not to have the 

 power of migration from one leaf to another, but in such an 

 event they emerge as imagos dwarfed in size. As we find with 

 many other larva) living in the interior of leaves or branches, 

 these have a horny plate on the second and third segments, 

 which serves as a shield; the head is brown, the body white, 

 with a greenish tint down the back. They are well provided 

 with legs, having no less than twenty-two ; these are either 

 banded or dotted with black. It is singular that being so well 

 able to move from place to place, these larva? should be de- 

 termined to make one leaf their home. They only quit it to 

 undergo the pupal change, when they bite a hole through the 

 epidermis, and descend to the ground, dropping, and not 

 crawling down as is believed. Having reached it they enter 

 and conceal themselves there, spinning a silken cocoon. 



Several things which are rather peculiar are noticeable in 

 the history of these little fellows. Thus, within their mines 

 they almost invariably lie upon their backs, and when young 

 are not easily alarmed, but when about half grown they race 

 up and down the mines if the leaf is handled, and when 

 nearly adult, instead of moving along, they alternately bend 

 and straighten then- bodies if alarmed. Of the frass (a conve- 

 nient German word which serves to veil what we would prefer 

 not to name in Anglo-Saxon), Mr. Healey states that " it is 

 found in little pellets, which are scattered about the mined 

 portions of the leaf, though instances occur where these pellets 

 of frass are connected together, reminding one of a string of 

 liliputian sausages. At certain times short lengths of the 

 cord of pellets break away from the main cord by their own 

 weight, and after a time the larva, as though animated by a 

 desire to keep its abode clean and tidy, is seen to go in search 

 of the hroken-off portions of frass, and by a few dexterous 

 movements of its posterior segments to collect and arrange 

 them into a circular-shaped heap." 



Other saw-flies of larger proportions are found on the Birch 

 occasionally, feeding externally in groups in their customary 

 manner, such as Cimbex femorata and Trichiosoma sylvaticum. 

 These may be got rid of or checked; not so the leaf -miners, 

 which baffle our skill, as we scarcely observe them until the 

 mischief is done. Nor is the Birch without its aphis and 



