S6S 
THE TROPICAL AGRICULTURIST* [February i, 1890. 
with stimulating manures, and with every obstacle or 
check, to root extension carefully removed, and then 
to profess to marvel greatly that Nature returns us 
for such food-gorging conditions great crops of wood, 
chiefly — or only. 
Had fruit growers learned more, and to better pur- 
pose, the great lessons that Nature teaches, in almost 
any natural soil, even the artificial practice of root- 
pruning might never have been needed. For the 
natural checks to growth caused by scarcity of plant- 
food are intended to cbeck growth and establish and 
maintain a high state of fertility. 
Forgetting these lessons, the cultivator who has 
over-manured, and so over-fed his trees, with the one 
hand, nas been compelled to prevent their consuming 
it to excess by pruning off a large portion of their 
roots with his knife in the other. But whether 
practised by Nature or art, the object aimed at in all 
root-pruuiug alike, is the enhancement of fertility by 
reducing excess in the food supplies. In the manipu- 
lation of the roots, either by Nature or art, for this 
purpose, we gain secondary advantages of equal, or even 
more importance than the primary one. These have 
been briefly referred to as improving the quality of 
food supplies. Without going into minute details, no 
one conversant with the more obvious and immediate 
effect of root-pruning will deny that it metamorphoses 
pipe-like roots into masses of fibres. Further, all 
practical fruit growers agree that in these fibrous roots 
the basis of fertility is laid, and the habit of continuous 
fertility perpetuated. 
But not only does root pruning change the character, 
but the situation of the roots; generally it raises 
them nearer to the surface, exposes them to more 
heat, and brings them into contact with sweeter— that 
is, better and more immediatly available food. 
Tnat much may be done through raising roots to 
more genial plains or fields of labour, is abundantly 
proved by the mere act of root lifting, where little or 
no, or as little as possible, of root pruning has accom- 
panied the process. Barren trees have thus been made 
fruitful, cankered stunted trees become clean, and 
grown into robust health by thus forcing the roots to 
gather their food closer to the surface. By these and 
other methods, the root pruning, readily and 
necessarily, limits the supplies of food and improves 
its quality, and by both processes they succeed in estab- 
lishing and perpetuating fertility. Much of success or 
failure, however, in these great culture and productive 
achievements, depends on the times, modes, and extent 
of rooting and pruning, and hence a second article 
may profitably be devoted to practical instructions on 
these important matters. — D. T. F. 
[The practical results of root-pruning are obvious. 
The benehts of the process when judiciously performed 
are also obvious. But while in our present state of 
nescience we should hesitate to supply anv ■ ther ex- 
planation of the causes of the |good result ban that 
turnished by our correspondent, we are by juo means 
satisfied that he is correct. The increased production 
of fibrous roots resulting from root-pruning, so far from 
limiting the supplies of food must surely increase 
them, though it may regulate and diffuse the current 
of absorbed liquids. Again, the use of the word fertility 
in this connection is misleading. The growth of what 
we call the fruit is not necessarily an evidence of ferti- 
lity, but only an extension of the vegetative growth by 
which leaves and shoots are formed. Real fertility 
consists in the development and ripening of the seed 
and of the embijo plant within it, which is another 
matter. — Ed.]— Gardeners' Chronicle. 
diseases" OF PLANTS. 
Bv H Marshall Ward, m.a., f.r.s , f.l.s. Romance 
of Science Series. Published by the Society for Pro- 
moting Christian Knowledge. London, 1889. 
The studeut of botany fifty years ago devoted Ins 
energies almost exclusively to the collection of speci- 
mens • to him the formation of a "Hortus siccus was 
the great object to be attained ; while " life history 
was as unfamiliar a term ae " biology." During the 
latter half of the present century a complete chang 
has come over the botanioal world. The younger 
botanists now turn their attention more and more to 
tbe study of the phenomena of life, which their pre- 
decessors so much neglected. Perhaps the advent of 
the Potato disease in 1845 had as much as anything 
to do with the popularisation, so to speak, of the 
study of plant diseases. The past generation of bota- 
nists troubled themselves very little as to how a plant 
lived, still less how it died. In this country we are 
yet far behind our continental brethren in the study 
both of biology and vegetable pathology. This has 
arisen from a variety of causes, such as the want of 
proper laboratories for botanical work, the lack of 
students willing and able to take up such investiga- 
tions, but to a very large extent it has been owing 
to an absence of books treating of these subjects in 
our own language. 
Foremost amongst the workers in this field of study 
stands the author of the book before us, and we 
heartily congratulate him upon the excellent little 
manual of Plant Diseases he has just published. Mr. 
Marshall Ward has produced a verv readable and a 
very instructive book, treating of several of the more 
common and typical plant diseases, in such a manner 
that anyone who wishes to do so can understand all 
the main points connected with their production, their 
development, and the best available means of com- 
bating them. 
Although one might think otherwise from its title, 
only those diseases of plants cauBed by fungi are 
treated of. The twelve chapters of which it consists 
are all of them worthy of careful perusal. Tbey 
inolude the damping-off of seedlings caused by Pythium 
De Baryanum, Finger and Toe (Plasmodiophora 
brassicae, the Potato disease, smut, bladderplums, the 
Lily disease, ergot, the Hop disease, and tbe rust of 
Wheat. Each of these subjects is treated of thoroughly 
and clearly from a biological stand-point. In tbe 
chapter on the Potato disease, a subject which has for 
so many years been the battle-ground of investigators, 
and which is consequently a very thorny subject, the 
author has succeeded in keeping clear of partisanship, 
and has given a lucid and exact account of the disease. 
In spite of all the work that has been done, there are 
yet many points connected with the life-history of 
Phythophora infestans that would repay investigation ; 
for instance, the duration of the vitality of the conidia 
under various degrees of dryness. The duration, too, 
of the vitality of the mycelium, both in the stems and 
in the tubers, is more taken for granted than demon- 
strated. We think the author has dismissed some- 
what too summarily the possibility of checking the 
ravages of the disease upon the foliage by external 
remedies, such, tor example, as the copper-salts, of 
which French mycologists speak so highly. 
The title of Chapter XL, i: The Rust of Wheat," is 
not happily chosen, as in this country the rust stage 
of the ordinary Wheat mildew, of which the chapter 
treats, is not by any means so prominent a phase as 
botanists would have us believe. 
The Lily disease is, of course, treated by a master 
hand, and for the rest of the book we can find nothing 
but praise. — Gardeners' Chronicle. 
Tea Culture in Natal progresses but slowly 
to judge by the report on page 564 of the 
proceedings at a recent meeting of the Natal Tea 
Company. In South Africa as in Russia, it will 
soon be found that it is more costly to grow 
tea than to import the pure article from Ceylon. 
Mica. — I hear that the mica trade for electrical 
engineering purposes is just now very brisk. One 
of the London houses, Messrs. Wiggins & Son, 
at present executing a large number of orders for 
electrio companies in England and on the Continent, 
— Our American contemporary, Modem Light and 
Heat, states that a patent has recently been 
granted to the Gould & Watson Company, of 
Botson, for the use of flake mioa in electrical 
conduits. The system briefly consists of a box 
tube or eleotrical conduit, into which the wires are 
drawn, the conduit itself being filled and packed with, 
flake mioa,— Electrical Trades Journal, 
