.208 



THE TROPICAL AGRICULTURIST. 



[September i, 1883. 



themselves. The tnugus was ii>iiirisoiu-il witliin tliose bills 

 by tbe hot air which for himtlreds of miles sui-rouuded 

 them ou all sides. ^\■hen the Potatos were introduced 

 into North America and Europe the parasite was separated 

 from its host, for, under ordinary circumstances, neither 

 the mycehum nor the simres can be sent through the torrid 

 zone without losing their vitality. The .separation between 

 parasite and host lasted till about 18-10, i.e., about 300 

 years. The employment of steamers (for before 1840 the 

 numbir of tteamers was but very smaU), the great guano 

 traffic which sent many ships to the kingdom of the Potato 

 foe— tlie employment of ice perhaps— for by the means 

 of ice the Potato fungus can be sent anywhere,— all these 

 circui.istauces were favourable to the transmission of the 

 disease to the temperate countries of the northern 

 hemisphere; in fact it is simply warmth that for 300 years 

 separated the fungus from its host. The same separation 

 can with complete certainty be effected now in the course 

 of a few hours by means of an elevated temperature 

 applied to the seed Potatos without injuring their growing 

 power in the least. To make the process practical, Mr. 

 Jensen employs a comparatively high temperature ; but 

 witli a lower temperature the same result can be obtamed, 

 only it requires to be applied for a longer time. Certain 

 precautions are necessary to prevent injury to the Potatos, 

 but these can be easily met by a suitably constructed 

 apparatus which Mr. Jensen has devised. These discoveries 

 ha\-e been communicated to the Soeiete Natiomde cV Agri- 

 ctiltiire de Frniice. The distribution of the disease is more 

 dependent on the mean maximum temperature in summer 

 than on the mean day temperature, hence the disease does 

 not go so far south "in continents as on islands. Speak- 

 ing generally, the disease does not exist in continental 

 lowlands in the northern hemisphere to the south of the 

 fortieth parallel of latitude; the disease does not exist in 

 tropical countries where the mean temperature amounts to 

 25'= C. (77° Fahr.) for any considerable time durmg the 

 year. It is not found in mountainous districts within the 

 tropics, except under very rare circumstances, because its 

 introduction to such places is very difficult. It probably 

 exists in all countries with a temperate or cold chmate in the 

 northern hemisphere where Potatos are grown. It may be 

 found in temperate climates in the southern hemisphere. It 

 is not fomid in Au.stralia, although in many parts of that 

 quarter of the world it would thrive if introduced. 



Eespectiug the influence cf an elevated temperature upon 

 the development of Peronospora infestans, I have only one 

 word to add, and that is to draw attention to the way in 

 which it thrives upon outdoor Tomatos in this country com- 

 pared to those gro\vn mider glass. 



In conclusion. I may say that the above is collated from 

 various papers and circulars of Mr. Jensen and from private 

 letters written to me. I only wish he had found some one 

 better able to express his views and place the result of his 

 labours in a more lucid manner before the British reader. 

 Charles B. Plowright.— Gardenei-s' Chronicle. 



C.4ENADB\, OB SroNEWAX.— This peculiar wax is mtensely 

 hard, and its melting point very high— too high for utiUty, as 

 regards caucUes at least (1S5 ° F.). It is, however, I beheve 

 used largely on the Continent as an adulterant, or, perhaps 

 Icitimately, a hardening mixture, and enters largely into the 

 comi>nsition of varnishes, heel-balls, &o. The colour varies 

 from light yellow to deep gray green, and it can be 

 bleaclied to an intense white. Oarnauba wax is found adher- 

 ing as a tbin film, like varnish, to the leaves, stalks, and 

 the berries especially, of a BraziUan palm, the Coperiiicia 

 cerifa-a. From these the wax is boiled oft, and skim- 

 med into moulds. When congealed, its likeness to stone 

 is so great that, were it not for the low sp. gr. (999), one 

 might easily class it with minerals. The composition of 

 stone-wax is very uncertain. Lewy, a great authority on 

 waxes, finds it to contain 80 per cent, of carbon; and Allen 

 vouches for the presence of a notable quantity of free myri- 



cyl or melissic alcohol CiSO H^ } O. The quantity pro- 

 duced is very large, but 1 am not in possession of trust- 

 worthy statistics. 



The next, and last, of the true waxes is J/i/rtle wax (My- 

 rica tallow). This soft green substance is formed on the 

 berries of the Mt/rica cerifei-a, an American tree shrub. 

 The berries grow in small clusters along the stem, 



and, when ripe, are covered with a tolerably thick rind of 

 the wax, which is removed by boiling. This substance is 

 also used chiefly in adulteration, though, from the very low 

 melting point (123 = F.), the use must be limited. The 

 composition is chiefly palmitic and myristic acids, with a 

 httle glycerine, but has never been accurately determined. 

 Japan wa.v, also called " tree wax," ought properly to rank 

 as a fat, being a palmitate of glycerine, which latter it yields 

 upon saponification. It is derived from the roots of several 

 trees of genus Rhus, chiefly from the Shits succedanca of 

 the East Indies. The use of this wax as an adul- 

 terant is checked by its disagreeable odour — otherwise, it 

 is a very useful substance ; it enters largely mto the com- 

 position of vegetal ';! wax candles; much used as a sub- 

 stitute for those of genuine bees-wax. Its sp. gr. is about 

 •999, the m.p. 120 ° F. There are several other waxes, of 

 great use in their native countries, as pnZm wax; from the 

 ! stem of the Gefoxylon aiidicola, Brazil, and pcuha wax, from 

 the Mip'lca ocuha of the same country; also Andaquies wax, 

 Cuba wax, and others of uncertain animal origin. The two 

 fh'st-named furnish a large portion of the candle power of 

 northern South America. — Journal of the Society of Arts. 



Chinese Tea Tkade. — Tlie retm-us of the export of tea 

 from China and .Japan during the past season contuiue to 

 show a great dechne in the shipments to this country. In 

 the twelve mouths ending the olst May, the total consig- 

 nments to us were in round numbers: — 



lb. 



18S2-3 170,000,000 



18S1-2 ie4.0(X),000 



18S0-1 175,000,010 



To the Continent the shipments were — 9,360,000 lb. in 18S2-3, 

 as comp.ared with 10,100,0001b. in 1881-2, and 7,200,0001b. 

 in 18S0-1. Accompanying this decline in the suppUes of tea 

 which Europe has obtained from China, there has been a 

 large increase in the svipplies from India, and the Indian, 

 product would thus appear to be gradually ousting that of 

 China from our markets. — Journal of the Societi/ of Arts. 



Mr. Herjlvxn Huller, the distinguished German natural- 

 ist, who has made the cross-fertilisation of flowers, and the 

 insects which perform this work, his special study, has very 

 clearly explained why such flowers as the well-known lung- 

 wort (PulmonariaofficinaUs) and others of the same natm-al 

 order have two colom-s, red and blue; the former colour 

 is generally assumed first, and the latter as the flowers 

 get older. He proved by examination that all the blue 

 flowers of the lungwort were empty of honey, and the stig- 

 mas of their pistils were supplied with pollen. Mr. Miiller 

 concludes that the blue colours of tbe older flowers of the 

 lungwort, whilst increasing the conspicuousness of the clu.s- 

 ters of flowers at the same time indicate to intelligent bees 

 to which plants they should restrict their visits, to their 

 own. as weU as to the plant's profit. Verily the more in- 

 timately we are acquainted with the biological relationshipsof 

 flowers, the more do we discover that "every freckle, streak, 

 and stain" has a distinct meaning, and bears some active 

 relation.ship to the well-being of the plant. In some instances 

 the colours and markings may even remain for some time 

 after their real cause for existence has ceased. — Australasian. 



Jamaica: — Cinchona Plantation, Gordon Town. — Shortly 

 after I sent you the specimens of "Native bread" so kindly 

 noted at p. 472, vol. xix., I placed some of them in a pot 

 of ordin.ary potting mould, and I have discovered that they 

 are covered with mycelium, issuing from the tuber in a similar 

 form to the roots of a Gloxinia, and on the side where they 

 are somewhat indented, there is issuing a growth in ap- 

 pearance similar to sketch. This m.ay be only a stronger 

 mycelium growth, and as yet it is hardly enough developed 

 to judge or hazard an opinion <as to what it may become. 

 I have sketched tbe size of the tuber as accm-ately as possible. 

 On examining a tuber which had been broken, I find it to 

 be covered on the broken part with a growth very similar 

 to the substance of a Polyijorus, which, though quite white 

 when uncovered, became in a few minutes of a yellow tint. 

 The tubers are placed for observation in a temperatiu*e 

 under glass from 6-5 ° to 75 ° Fahr. I shaU watch with 

 much interest the further groivth of the mycelium, and 

 should you desire it, wUl inform you of the result of the 

 observation, and I woLdd willingly undertake to perform any 

 experiments you might suggest to further my research. — F. 

 Hakt, Superintendent, Government Cinchona Plan^ition. 

 — Gardeners' Ohronicle. 



