462 



THE DICTIONARY OF GARDENING, 



Oak continued. 



seldom doing very great harm to the latter; yet even 

 they may at times do great damage to Oaks, such as 

 the larvae of various moths (see Hybernia, Lackey 

 Moth, Liparis, Orgyia antiqua, &c.) to the leaves; 

 Cockchafer grubs, Mole Crickets, &c., to the roots ; Bala- 

 ninus nucum, or Nut-Weevil, in the fruit, &c. It 

 may, indeed, be said that no part of the tree is safe 

 from the attacks of insect foes; but it is impossible 

 here to do more than mention a few of the more in- 

 teresting and important of these. Several beetles (see 

 TomicicUe), e.g., Platypus cylindrus, Xyleborus di-yo- 

 graphus, &c., and some moths (see Goat Moth) bore 

 into the wood, and render it unfit for use ; but, for- 

 tunately, they seldom attack healthy trees. As a pre- 

 caution against them, all the dead trunks should be re- 

 moved, and dead branches should be destroyed. The other 

 moths above mentioned are hurtful by consuming the 

 leaves of Oaks, Beech, and many other trees. But 

 even more thorough in the extent of its ravages is a 

 small moth (Tortrix viridana), which almost restricts 

 itself to the common Oak. It reaches about in. in the 

 spread of the front wings, which are green. The larvae 

 live for a time in the buds, then in the leaves, and 

 pupate in leaves spun together, or in the soil. In some 

 seasons, and in certain localities, hardly a leaf is 

 allowed to remain on the trees. Shaking the branches 

 over sheets laid on the ground will cause the larvae of 

 all the moths to fall on to the latter, from which they 

 may be swept up and destroyed. The same method may 

 be employed for the capture of various kinds of small 

 beetles, chiefly Weevils, that gnaw the leaves and buds, 

 as well as of Cockchafers, which, at times, do consider- 

 able damage to the trees. 



The leaves are frequently mined by the larvae of small 

 moths and beetles, but the injury from this cause is 

 too slight to call for discussion at present ; and, for 

 the same reason, the larvae that feed in the buds may 

 be passed over in silence. Among the more frequent 

 causes of injury to the acorns is the beetle Balaninus 

 nucum (see Nut- Weevil). Numerous species of Green 

 Fly attack the Oak, and, at times, must weaken the 

 trees very greatly, covering the lower leaves with honey- 

 dew, among which grows the Fungus Capnodium quer- 

 cinum (see Oak Fungi), which may, in some cases, 

 prove hurtful to the trees. But, of all the insects that 

 attack Oaks, probably the most striking, in respect to 

 the effects produced by them, are the makers of the 

 various Galls so frequent and BO noticeable on Oak 

 trees. See Oak Galls. 



OAK APPLE. See Galls and Oak Galls. 

 OAKESIA (of Tuckerman). A synonym of Corona. 



OAKESIA (of Watson). Included under Uvularia 

 (which see). 



OAK FERN. See Polypodium Dryopteris. 



OAK FUNGI. The species of Fungi that live upon 

 the common Oak are numerous; but by far the larger 

 proportion either do comparatively little injury, or make 

 their appearance only on dead parts of the trees; e.g., 

 on bark or wood of dead branches, or on leaves or 

 acorns. Many of the species are very minute, but only 

 a few of the more injurious will be mentioned here. 

 Those of chief importance belong to the Hymeno- 

 mycetes (see Mushrooms), and, for the most part, to 

 the genus Polyporus, which has pores instead of gills on 

 the lower surface of the cap, or spore-producing struc- 

 ture. The .following are among the more noteworthy 

 species, inasmuch as their mycelium traverses the living 

 wood of the Oak, and withdraws the nourishment from 

 the cells of the wood, which, in consequence, becomes 

 decayed and brittle. The cap, in most of the species, 

 grows to a breadth of several inches. Oi Polyporus, 



Oak Fungi continued. 



several species attack living wood of Oak, e.g., P. 

 dryadeus, P. sulphureus, P. igniarius, and P. inty- 

 baceus ; so also does the nearly-allied Fistulina hepa- 

 tica, or Beefsteak Fungus. In each case, the mycelium 

 of the Fungus usually gains entrance by the uncovered 

 end of a branch, or a wound, and spreads through the 

 wood cells. Careful pruning, and protection of wounds 

 by tar, or some other dressing, are of very great service 

 in preventing the entrance of mycelium, and the conse- 

 quent development of the Fungus, with its disastrous 

 results to the trees. The methods of pruning, and of 

 protecting wounds, cannot be treated of under this 

 head, but will be found fully described in this work under 

 the appropriate headings. Trees suffer much injury 

 from Fungi in their roots, which become attacked by 

 the mycelium spreading in the soil from adjoining roots 

 of dead trees; hence, care should be taken to remove, 

 as far as possible, all decaying wood from soil in the 

 neighbourhood of healthy trees, lest the Fungi should 

 extend to the roots of the latter, and, after a time, 

 cause their destruction. Trees, when badly attacked 

 by these Fungi, should be cut down and destroyed, to 

 prevent the spread of the Fungi to healthy trees. See 

 Polyporus. 



A soot-like crust very frequently covers the leaves of 

 Oaks, as well as of many other trees and shrubs. When 

 examined microscopically, it is seen to be formed of 

 cells and threads of a Fungus, belonging to a group 

 included under the name Fumago, called also, when 

 fully developed, Capnodium. In Capnodium, the spores 

 for reproduction are produced in the interior of 

 larger cells (asci), many of which are inclosed in a 

 globular or flask-shaped vessel (perithecium), of micro- 

 scopic size ; but this stage of development is not often 

 met with. The Fumago stage is much the more com- 

 mon. In this, the reproductive cells are separated from 

 the tips of threads on the exposed surface, or are pro- 

 duced in minute flask-like perithecia, but not in asci. 

 The crusts are much like soot in general appearance, 

 like it, resting only on the upper surface of the leaves. 

 They have frequently been attributed to injury from 

 smoke, leading more than once to lawsuits for com- 

 pensation for such alleged injury. The microscope shows 

 the cell walls to be dark brown. 



The Fungus is readily removable from the leaves by 

 rubbing the surface. It does not seem to derive 

 nourishment from them at least, to any marked extent 

 but feeds in large degree, probably, on the honey dew 

 excreted abundantly by various kinds of Aphides, or 

 Green Flies. As these insects live on the lower surface 

 of the leaves, their excretions fall on the upper surface 

 of leaves below them, which explains the presence of 

 the Fungus on that surface. If present only in small 

 amount, the crust does not seem to do much injury to 

 the trees ; but when thick, it partially chokes the leaves, 

 and cuts off the light from them, so that they become 

 sickly, and fail to nourish the trees. This seldom occurs 

 before autumn, which is fortunate, as there is hardly 

 any practicable method of removing Fungi from trees 

 such as Oaks. The species found on Oak has received 

 various names, that generally adopted being Capnodium. 

 quercinum. 



OAK GALLS. Very noticeable, because of their size, 

 the peculiarities of their forms and colours, and the dis- 

 tortions and alterations that they occasionally produce 

 on various parts of Oaks, are the Galls, so frequently seen 

 by even the least observant spectator who passes an Oak- 

 tree in autumn. The development of the Galls, and of 

 their makers, is now believed to be very peculiar in 

 certain respects in the case of most of them ; but only 

 a few of them are here selected as examples. Galls are 

 new structures budded out from stems, leaves, or other 

 parts of plants, under the influence of a stimulus applied 



