GLOSSARY. 



397 



wood, aijpears also as a parasite and corrodes 

 the wooil. It attacks the horse chestnut, 

 the maple, the ailantus. Its myceliuna not 

 only extends into the bark but into the wood 

 itself ; it is a parasite of the ligneous body 

 like the polypone, which live at the expense 

 of the starch. The corroded wood no longer 

 serves for the passage of the sap and the 

 tree dies eventually. In the autumn this 

 disease is easily recognized, for there is seen 

 to appear, across the dead bark, cushions of 



stroma Wllich b.Tolu,- r.,VCV,-d witli r,,iudi,l 



on which the in-vitli.-ra aiv ],r.),luir(l. This 



visible form is t.-niird T,'hr,rnh,ri,i n,l<i.,ns. 



NeCTHIa DITISSIMA ((•;illl<iT iif tl[r .-Iplilc- 



tree, thc|,c;ii--trrc,;Mid tli,- 1,.-.t1i). -■['his liui- 

 gus is tlic immediate .MUse of some eaiikers 

 whi'-li gnaw the branches of tlie apple-tree 

 and the pear-tree. It is one of the most for- 

 midal)le diseases of fruit trees. Cankers are 

 generally bonlered with small coral red points 

 which are the peritheca of the fungus ; they 

 form real wounds in the bark which do not 

 cicatrize and wliich always extend and sink 

 <leeper and deeper. On the edges of the 

 wound the still healthy tissue forms swell- 

 ings, Ijut these are rapidly destroyed by the 

 fungus. Tills corrosion hinders the circula- 

 tion of the sap, the trees languish, become 

 covered with dead wood, and produce no 

 more fruit. The first phenomena explains 

 itself on the outside by a point of bark which 

 lieeonies de))ressed, forms concentric fissures 

 and eanscs tlie bark to tear, which falls in 

 strips. 'I'lic mycelium is not only found in 

 the l>:irk but in the ligneous body and in 

 the interior of the vessels, and the cells of 

 the ligneous parenchyma. It multiplies in 

 the midst of the disorganized tissues. The 

 woolly aphis prepares the way of access to 

 this fungus. 



Nematodes Injurious to Cultivated 

 Plants. — These are small worms of a filiform 

 aspect, a smooth tegument, which live in the 

 interior of plant tissue, causing character- 

 istic deformations of the organs attacked. 



Nematus ventricosus, Nematus ribis 

 (gooseberry saw-fly). — The larvae of these 

 saw-flies attack different species of goose- 

 berries, entirely deprive these shrubs of their 

 foliage, and thus prevent the development 

 of the fruit. During May the larva which 

 is adult descends into the ground to turn 

 into a grub. After three weeks the insect 

 hatches and forms a new generation. 



Noctua: Agrotis, Mamestra, Plusia. 

 — The noctua are moths, they are not so heavy 

 as the bombycides. The wings are char- 

 acteristic ; the upper, darker than the lower, 

 have two spots. The caterpillars are glab- 

 rous, greyish ; they do not spin a cocoon, they 

 pass into chrysalides in the soil. 



Noctua gamma, Plusia gamma.— Grey- 

 ish-brown moth of 4 centimetres with a 

 silver spot which represents the Greek letter 

 Gamma on each of its upper wings. The 

 moth flies in the daytime, the green cater- 

 pillars have an appearance which recalls the 

 citigrade spider. They attack leaves of the 

 most different nature : cabbage, beet, potato, 



colza, lienip, flax, maize, peas, beans ; there 

 may be two or three generations a year. 



Noctua of the Lettuce. Polia dysodea. 

 — Noctua, the wings of which are of a greyish - 

 white with more or less dark-coloured bands 

 and spots. The caterpillar of pale green 

 with three dorsal, longitudinal brown stripes, 

 gnaws the leaves and the seed of lettuce. 



Noctua of the Pine. Tmchen pini- 

 jifrda. — Butterfly, 1| centimetres long, head,, 

 thorax, and upper wings, red, with yellowish- 

 wliite sp.itsaiid lines on the latter. The ab- 

 d'liiirii ,111,1 the lower wings greyish-brown. 

 The female lays in April on the needles of 

 the Funis sylvestris (Scots pine). The cater- 

 pillars attack the young shoots ; they are 

 green with white and orauge longitudinal 

 bands ; they reach 3 centimetres in length in 

 July ; they turn into chrysalis in the moss- 

 at the foot of the tree and there pass the 

 winter. 



OiDiUM OF the Vine. Uncinula ameri- 

 cana, Oldmm Tuckeri. — The myceliam of 

 this fungus lives on the surface of the plant 

 and draws its nourishment from the cells of 

 the epidermis by numerous suckers. The 

 organs attacked are rapidly altered, the ex- 

 tremities of the young shoots wither, the 

 leaves shrivel up and die, but the effect is 

 still more deadly on the grapes, which crack 

 and rot. The oidium, which is propagated 

 by its conidia during the whole growing 

 period of the vine, may entirely destroy a 

 crop. The worst attacked plants may, how- 

 ever, again become vigorous if the disease is 

 arrested in time. The oidium may be recog- 

 nized by the white or greyish efflorescences 

 on the parts attacked. The oidium first ap- 

 peared aljout fifty years ago. The ilisease ap- 

 pearetl to attack certain varieties of vines with 

 a black grape. La Folic Blanche of Char- 

 entes and Armagnac was not attacked until 

 five years later. Owing to the oidium the wine 

 crop of France fell from an annual produc- 

 tion of 50,000,000 hectolitres (1,100,000,000 

 gallons) to 22,662,000 hectolitres (498,.^)64,000 

 gallons) in 1853 to 10,824,000 hectolitres 

 (238,128,000 gallons) in 1854. This produc- 

 tion was the smallest of last century, for 

 even in the acute period of the phylloxera it 

 was not reiiuced below 25,000,000 hectolitres 

 (550,000,000 gallons). 



Opatkum sabulosum.— This insect of the 

 faniily of tenebrionides appears in May. It 

 attacks the buds of grafts from American 

 stocks, especially when they are earthed up. 

 The larva? live two years in the soil. 



Ophiobolus graminis (disease of the 

 lower part of the stem of wheat). — Laid wheat 

 is due to the invasion of the winter nodes 

 nearest the soil by a fungus which, in damag- 

 ing the stalk at the level of the soil, is often 

 the cause of the laying of the straw of 

 cereal crops. The mycelium develops in 

 the interior and the exterior of the tissue. 



Orobanche minor (orobanche of clover, 

 broom rape). — The orobanches are para- 

 sitic phanerogams of the roots. They live 

 exclusively at the expense of the plant on 

 which they graft themselves for they are- 



