Peronospora 



( 1T9 ) 



Petalacte 



two year old plants seldom, hut older ones are 

 the usual prey. The removal and burning of the 

 tup 2" or 3" of soil is to be recommended, also 

 the frequent planting of beds. 



Varifgaiia attacks the leaves of Roses. The 

 lami- should be sought for and killed, and the 

 lui.-hes syringed with Quassia chip solution, (.^e; 

 [N8BCTICIDBS.) 



PERONOSPORA. 



A large genns of parasitic, microscopic Fungi. 

 They belong to the group of White Moulds, which 

 is again included amongst the Mildews. Until 

 recent years the fungus causing the Potato disease 

 was accounted a Pcionospora. hut it is now referred 

 to the allied genus Phytophthora, which see. 



The mycelium (vegetative portion) of these Fungi 

 runs internally through all the parts of the hosts, 

 from roots and tubers to leaves and seeds, making 

 free with the nutriment the cells contain. Their 

 course is afterwards marked by softness and 

 putridity of the tissues. 



Methods of propagation are as follow. When 

 the fruiting stage is reached, numbers of arms 

 (eonidiophores) are produced at right angles to the 

 epidermal tissue of the host, and externally. These 

 branches bear a number of fruits (conidia). The 

 first stage in the germination of these conidia is 

 that each one divides into a number of cells 

 (usually five or six), each containing a zoospore. 

 The-e zoospores are motile, being furnished with 

 two hair-like appendages (cilia), by which they 

 swim or creep. The zoospore, on germinating, gives 

 rise to new mycelia. This is the summer stage 

 of reproduction. Conidia and zoospores are very 

 senMtive to cold, and towards winter a sexual 

 process gives rise to an egg, or resting spore 

 (oospore), which, with its thicker cell wall, can 

 resi.-t cold, germinating in the spring. 



Remedies. It is necessary to catch the spores 

 whilst on the outside in other words, prevention 

 rather than cure. Suggested items are : 



1. Spraying with Bordeaux Mixture, potassium 

 sulphide solution, or ammoniacal solution of copper 

 sulphate (see FUNGICIDES). 



2. The destruction of badly infested plants, 

 roots, and tubers. 



'.'>. Thorough cultivation of the soil in autumn. 



1. Selection of vigorous seed stocks. 



"). An occasional change of stock. 



6. To encourage continuous and healthy growth, 

 to avoid checks, and extremes of drought and 

 moisture, which weaken the constitution of the 

 plants, and thus render them liable to infection. 



Principal Species : 



url.nrescens. Attacks rots, Parsnips, Parsley, 



Puppies only, caus- and many other Um- 



ing distortion in the bellifers. 



^tems. parasiticii. Destructive to 

 Cactorum. Causes decay Turnips, Cabbages, and 



in many species of the larger Cruciiers. 



cultivated Cacti. pygmsea. Parasitic upon 

 effusa. Attacks Spinach ' Anemones. 



and other members of Schachtii. Destructive to 



I 'hciiopodiacoie. Beetroot. The myceli- 



gangliomformu. Attacks um lives in the roots 



Lettuces and many through the winter. 



Composite ; is getting Seeds are also affected. 



rather common. schleideniana. Attacks 

 infcstans. Potato dis- Onions and other Lili- 



ease ( Phytophthora accous plants. 



iiifestans). sparsa. Roses. No 

 nivea. Preys upon Car- oospores yet discovered. 



Probably confined to 

 Xorth America and 

 Continental Europe. 



Vicise. Peas and Vetches. 

 One of the most trouble- 

 some. 



viticola. On Vines. 



PE RSE A. (AVOCADO or ALLIGATOB PEAK.) 

 Many species in this genus (ord. Laurinese) of 

 stove trees or shrubs have large, fleshy, and edible 

 fruits. That of gratissima, the Avocado or Alli- 

 gator Pear, is about 6" long, lias a buttery flavour, 

 and is a common article of food in the West 

 Indies. Condiments are commonly used with it. 

 Propagation, by matured shoots in sand in bottom 

 heat. Soil, equal parts of fibrous loam and peat, 

 with sand. Firm potting. 



Principal Species : 



gratissima, 25' to 30', st., hai'd and prettily 



flowers grn., 4" across, grained (//. Tene- 



t'ruit Pear shaped. riffu; and Laurus in- 



indica, st., wh., wood dica). 



Other Species : 



carolinensis, 20' to 40', Laurus carolinensis). 



Jy., st., fruit bl. (syn. Red Bay. 



PERSIC A (.nee PEACH and 

 PRUNUS). 



PERSOONIA (synt. LINKIA and PENTA- 

 DACTYLON). 



Greenhouse shrubs or small trees (ord. Proteacese) 

 with yellow or white flowers. Propagated by cut- 

 tings of ripened shoots, in sand, under a bell-glass. 

 Soil, loam and peat in equal parts, with one-fourth 

 sand. Persoonia of Michaux is a synonym of 

 Marshallia ; and Persoonia of Willdenow a synonym 

 of Carapa. 



Principal Species : 

 ferruginea, 3', Je., shr., tree, yel. (syn. Drum- 



yel. mondii). 



lougifolia, 10' to 20', Jy., rigida, 3' to 4', Je., yel. 

 (syn. spathulata). 



Other Species and Variety : 

 hirsuta, 2' to 3', Je. , shr., nutans, 1', Jy., bushy 



yel. shr., yel. (tyn. flexi- 



lanceolata, 4', Je., shr., folia). 



yel., hairy. saccata, 2' to 6', Jy., shr., 



liEvis, a glabrous var. yel. (ai/ns. Fraseri and 



liuearis, 10 to 20', Jy., rnacrostachya). 



tree, yel. (syn. pinifolia Toro, sum., small tree, 



and pruinos'a). yel. (syn. Tora). 



PERYMENIUM. 



An obscure genus (ord. Composite) of no garden 

 value. 



PETALACTE (syn. PETALOLEPIS). 



A single species (oril. Composite) of greenhouse 

 evergreen sub-shrubs, of little value, but requiring 

 culture similar to the Helichrysums (which see). 



Only Species : 



coronata, 1', My., grh., wh. 



Persian, tfuris Eye (see Tulipa Oculus-fiolis). 

 1'i'f.tinniinn (v< JJiox/>yros riryiniaiui). 

 l'i ru Balsam Tree (see Myroxylo-n). 

 Peruvian Bark (tee Cinchona). 

 Peruvian Daffodil (see Jlymenocallis). 

 Peruvian Maslic (see Schinns). 

 Peruvian Nasturtium (see Tropeeolum tuterosum). 

 Peruvian ijn-amp Lily (see Zephyranthes Can- 

 dida). 



Pescatoria (see Xyi.iopetalum). 

 Pesomeria (see Pltaiug). 



