520 



A NEW TONIC FOR THE PEAR TREE. 



enters into the composition of a large num- 

 ber of plants, chemists have not yet told us 

 precisely what ofllce it performs. 



But since peroxide of iron forms a consid- 

 erable part — from 3 to 8 per cent — of near- 

 Iv all good soils, and since it is one of the 

 constituents of plants, it is evidently neces- 

 sary to their growth. We imagine it to 

 exert a direct influence on the healthy con- 

 dition and action of their green leaves. It 

 is evident, therefore, that if a soil becomes 

 exhausted of it, or if it is naturally deficient 

 in quantity, certain kinds of vegetation will 

 fail there, or succeed but imperfectly. 



Now the most serious obstacle to the cul- 

 tivation of the pear on the sea-coast, and 

 perhaps in certain soils in the interior, is a 

 kind of crack or blight, which affects the 

 fruit when half or two-thirds grown. The 

 green skin becomes rusty and discolored, 

 the fruit ceases to enlarge, the skin cracks 

 open, and is from that time worthless. At 

 the same time, or, as we have remarked, 

 often a little previously to this — the foliage 

 is also discolored with numerous russetty or 

 black spots — and the leaves become pale 

 green and rather thin in texture — in other 

 words, quite different from the thick deep 

 green foliage of a vigorous tree. They 

 usually drop from the tree, likewise, long 

 before the usual season. 



It is not difficult to see that this is in con- 

 sequence of a chlorotic or unhealthy state 

 in the cuticle of the leaf— which, having 

 lost its normal green colour, is no longer 

 able to obtain the requisite amount of car- 

 bon or nutritive food by the usual process 

 of decomposing carbonic acid. The same 

 thing is true of the fruit — the skin of which, 

 so long as it remains green, acts in precisely 

 the same way as the surface of the leaves. 



To restore the health of pear trees blighted 

 in this manner, it is necessary to restore the 

 healthy condition of the leaves. It is evi- 



dent from trial that the common manures 

 will not effect this, since these trees often 

 stand in gardens where the soil is annually 

 enriched. It is also evident that they have 

 exhausted something which the soil once 

 contained — for these same trees, or the 

 same varieties, once bore beautiful fruit and 

 healthy leaves in the same ground.* 



We are inclined to hope that iron, in some 

 of its forms, may prove to be the substance 

 in which those soils have become deficient ; 

 and that its judicious application may again 

 restore apparently decaying varieties to 

 sound health. 



We therefore solicit the attention of our 

 readers to the directions of M. Gris, on p. 

 471 of this journal, for the proportions of the 

 solution of sulphate of iron, so successfully 

 used by him, and we beg them to make 

 careful and repeated experiments with oxide 

 of iron. 



Perhaps the best form in which the latter 

 can readily be had, is in the sweepings and 

 cinders of the blacksmiths' shops, t and the 

 rust of old iron. As yet it is difficult to say 

 precisely what quantities should be used. 

 It must be remembered, however, that as 

 oxide of iron forms only a very small part 

 of the composition of plants, it must be very 

 sparingly used. We have seen half a peck 

 of the blacksmith scoria, (which it must be 

 remembered is in a good part composed of 

 other matters,) applied to a full sized bear- . 

 ing pear tree with good effect. Three or 



* Cultivators have conjectured that these varieties were 

 themselves "run out" or exhausted, and have abandoned 

 them for others. Any more vigorous sorts capable of making 

 healthier foliage, will undoubtedly succeed in such soils 

 where those of only ordinary vigor will fail. But it can not 

 be denied that some of the newest pears have also lately been 

 seen cracked and blighted in long cultivated soils on the sea 

 coast. 



t There are, chemically speaking, two oxides of iron — per- 

 oxide and protoxide. The colour of the former is blackish blue, 

 of the latter, red. The scales driven off red hot iron under the 

 anvil, are composed of peroxide and protoxide of iron. Iron 

 rust is chiefly peroxide of iron. 



