GLOSSARY. 



401 



are infected by the conidia which are de- 

 tached from the leaves and which are en- 

 trained on the roots by rain water. The 

 mycelium develops in the interior of the 

 organs attacked and gives off conidiophora 

 on the exterior of those on the under surface 

 of the leaves. The conidia which readily 

 become detached are summer spores which 

 may develop immediately, either by emit- 

 ting a germinative tube or in forming mobile 

 zoospores wliich fix themselves and soon 

 produce the disease. The Phytujihthora 

 may pass the winter in the tubers. The 

 Phytophthora is not propagated by means 

 of oospores from one year to another like 

 Peronospora. It passes the winter in a 

 hardy manner in the interior of the diseased 

 tubers. In spring it penetrates the nascent 

 shoots of these tubers. Such shoots remain 

 sickly if they are much infested by the 

 mycelium and sometimes have not the 

 strength to pierce the soil. On the some- 

 what vigorous shoots the mycelium forms 

 conidiophora early, the conidia of which 

 spread this dreadful vdisease over the whole 

 field. 



Potato Scab. — This is due to the growth 

 of an aerobic bacteria in the living tissues 

 of the circumference of the tubers. Under 

 the irritating influence of their development 

 the cells grow in an abnormal fashion below 

 the point of attack and form a thick crust 

 which greatly depreciates the market value 

 of the potato. 



PsiLA ROS^ (carrot-fly). — The larva of 

 this small fly, of not more than 4-5 milli- 

 metres, is black witli yellow head and legs. 

 It dwells in the carrot and there bores lioles 

 which cause the root to rot. The larvre turn 

 into grubs in the soil ; there are two genera- 

 tions a year. 



PsYLLA. — Hemiptera, distinguished from 

 the plant lice by the arrangement of their 

 legs which enables them to jump ; besides 

 they do not present asexual and sexual 

 generations, alternating the one with the 

 other ; they are all sexual. 



PsYLLA OF THE Pbar. Psylla PiH.— 

 This Psylla as well as Psylla piricola, which 

 are only to be distinguished from one another 

 by their different colour, cause great ravages 

 on pears. The Psylla appears towards the 

 end of May after having passed the adult 

 state in the anfractuosities of the bark. 

 After coupling, the female lays its eggs on 

 the leaves and young branches, which then 

 appear as if dusted with yellow. The 

 apterous larva? which hatch in a few days 

 pierce and suck the parenchyma of the leaves 

 and the young branches ; the latter especi- 

 ally bend and perish. 



Pyralides.— The Pyralides are micro- 

 lepi<loptera of larger size than the tortricides 

 and tinea ; their wings are of a triangular 

 form, the antenna long and pectinated. 

 The grubs though small cause considerable 

 damage. 



Pyralis of THE Apple-tree. Carpo- 

 capsa pomonella (apple-worm, codlin moth). 

 — Moth of ^1 centimetre long, ashy-grey 



wings striped crosswise with small dark 

 sinuous lines, with bronze reflex lustre and 

 marked at the extremity with a brown spot 

 encircled by a gilded yellow line. After 

 fecundation the female lays its eggs one per 

 fruit on the epidermis of the new-formed 

 fruit and on the surrounding leaves. In 

 about eight days tlie newly hatched small 

 caterpillar penetrates into the interior of the 

 apple. The fruit then becomes wormy. 

 There are two swarms a year. The cater- 

 pillar of the second swarm issues from the 

 fruit when the latter is ripe and passes the 

 winter for the great part under the bark of 

 the fruit tree where it spins a cocoon. In 

 the spring it changes into chrysalis. 



Pyralis OF THE Plum. Garpocapisafune- 

 hrana (wormy plums, plum worms). — Small 

 butterfly, 7 millimetres long, blackish with 

 some spots and lines of a greyish-blue. In 

 July the female lays its eggs on the still 

 green plum. As soon as hatched the cater- 

 pillars penetrate into the fruit and remain 

 there until maturity. Same habits as the 

 preceding. 



Pyralis of the Vine. — Tortrix, 1 centi- 

 metre long, of a more or less gilt yellow. 

 The butterfly flies in the end of June ; the 

 female lays 100-200 eggs on the upper 

 surface of the leaves forming a sort of 

 greenish-yellow plate. The eggs hatch in 

 the end of August. The caterpillars hiber- 

 nate between the fissures of the props and 

 under the bark in a small case of white silk 

 which they spin. la the following May 

 they quit their cocoons and gnaw the young 

 buds ; they agglomerate the small nascent 

 leaves with silk thread thus preventing the 

 buds from expanding ; moreover they en- 

 circle the small grapes with a silky envelope 

 inside which they shelter. The caterpillars, 

 reach 3 centimetres long, are green witli 

 very small whitish tubers ; the head as well 

 as the first ring are black. 



Rot. Rhizdctinia. — Parasitic fungi which 

 develop on plant roots, penetrate into their 

 interior, and kill them. Their vegetative 

 system is highly developed and enables them, 

 to pass in the soil from one root to another. 

 Sclerotes, sorts of tubers, enable them to livfr 

 a latent life when outside conditions are un^ 

 favourable to their development. 



Rot of the Heart of the Beet. Pleo- 

 spora putrefaciens.— The rot of the heart, 

 of the beet may be produced by several 

 fungi. That which is the most ordinary 

 cause is the Peronospora Sduichtii, which 

 directly attacks the small leaves of the heart 

 and covers them with a lilac flocked surface. 

 The Spluerella tabifica causes indirectly the 

 rot of the heart in passing from the petioles 

 of the largest leaves to the heart itself. In 

 both cases the heart leaves which are dead 

 are covered with a greenish-black coating. 



Rot or Moist Gangrene of the Potato. 

 —This disea.se is a complete disorganization 

 of the plant which is attributed to the action 

 of the Bacillus Amylobacter (Kramer) and 

 according to American specialists to the ac- 

 tion of Oospora Scabies (Thaxt). 



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