Supplement to the ^^Tropical Agricultm i»t" 
[Jan. 2, 1899. 
A very important commuuicatioii on tliis. sub- 
ject was read at the recent lIorticultLiri.1 Cou- 
}{ress at Taris, aud afterwards at tlie Ac.idcinic 
des Sciences. The author, M- JJaiiieJ, tiive.^ a 
rdsume of all the experimeii Is which he lias 
made relating to the reciprocal iiilluence of the 
scion on the stock and vice vcrnu, iMcludin<^ 
the effect on the taste and quality of the fruit. 
It is not possible to give more tlian tiie 
following abstract of the reuilt.>, which have 
• been published in detail in the Menvurcn of the 
National Horticultural Society of France: — 
( ; 1. The reciprocal iiirtuence of the scion ami 
of tiie stock cannot be denied, even though jl 
may not act with tlie same iuten.>ity. 
, ,2. This influence may bear on the general 
nutrition of the plant, and directly on its siz", 
vigour and resistance to parasites; or it in^iy 
affect the internal and e.viernal uiorpliological 
character of tlie plant, iiicliidiug itsorg.in'^ of 
reprcduclion, i.e., the fruit. 
3. Those variations are frequently of un 
hereditary character, and frequently appear dur- 
ing the course of tlie second generation. 
4. This effect of the gnift offers general practical 
advantitgos, viz., tlie j)roduction of larger tmd 
better fruit and vegetables (such as an improve- 
ment in their taste), and the direct production 
..of new varieties, e.// , a modification of the 
colour of flowers, of the shajie cf fruit, \c. 
5. The effect is more marked in lierb:iceous 
thaii in ligneous plant=, and on the prnyress 
.of the grafted plant than on the plant itself. 
C. The graft, which produces variation in 
the seed may be employed to pioihice new 
varieties. The variation may frequently be 
■ diverted culturally so as to impart almost 
<• .aissuredly, after repeated grafiing>, certain 
■ qualities (taste, colour, shape, &c.) to a plant 
■w hich did not originally possess them, and which 
varies easily under cultivation. As regards other 
plants, the graft still affords the means of ob- 
taining variation, however difficult it may be; 
and as soon as the change is observed, it can 
be pursued in the desired direction and wiili 
good results. 
THE IMPORTANCE OP HUMUS TO SOILS 
,! In an address on Green Manuring by Mr. J. W. 
Mills of the Pomona Expeii mental Station, the 
following facts were broug' t forward in support of 
the practice of green mannriiig as being t!ie 
■. ^08t satisfactory of all methods of maintaining 
• K^he fertility of the soil :— 
"At the Grignon Experimental Station in 
France, large glazed casks were placed on 
tripods in a diteli. The tops of the casks were 
on a ^level with the surrounding field so as 
to obtain, as near as possible, natural conditions. 
Vessels were placed underneath to catch the 
drainage water from the casks. Parts (some) of 
the casks were filled with earth from the field 
that had been fertilized with barnyard manuie, 
and parts (some) were filled with earth natiirally 
rich in humus. During one year the soil fertilized 
with barnyard mannre lost 51-7 grains of nitro- 
gen, while the soil rich in humus lost but 17 6 
grains. 
" In heavily-manured land \ to -J of the nitrogen 
that was made available was washed out in one 
year. If the uitrogea from tliie source is ao e ifi'y 
lost, we must look fur something udUitiouul tu 
supply our soils with humus and Jiitrcigen. 
Nitrogen from inorganic sources it uugily lott ttuil 
mineral manures never restore the original pro- 
ductiveness of Boil. It produces no humus, mid 
the loss of humus from poor sofl means its 
loss of jiower to refnin moisture and nitro- 
gen, and I lie loss of power to assimilate phos- 
phoric acid and potash and make it available 
to jdaiit growth. If humus is such a de^irable thing 
h't us look into the subj'-ct mid see how it gi-ts 
ill the soil througli nature. You have seen land 
that has given an abundant water supply by 
some new agency. It i)rodiice8 rank growths of 
vegetatio.n that fall down year after year. It is 
not long until the soil tnkes on a dark colour, and 
year after year tlie vegetation bepomes ranker 
aud more luxuriant. Some of onr richest land^ 
are formed in this way- What then csn we <io 
to our\--ulli vated laud tliat we may give it this 
life-giving element, humus "r Nature lets the 
weeds grow, but in most casfs we fight thtitn. 
It has been demonstrated that weeds not only 
supply humus, but during their life they help to 
retain in the soil that most evasive and subtle 
clement, niirotjen. 
'•At the Orignon Experimental Station casks weie 
filled with the same sort of soil, in part of these 
quick-growing crops, such as mustard and rape 
were grown, while in other casks nothing was 
allowed to grow. It was found that tiie soil in 
which nothing grew lost five times as much 
nitrogen as that iti which the plants were growing. 
The cu'ch jilants save the nitrogen in the soil in 
two ways: Firstly, using up the nitrogen as 
fust as it is made available; and second, by taking 
up a large part of the water and evnporaling it 
through their leaves, instead of letting it pass 
througli the soil and take the nitrogen with it."' 
The growth of ordinary grass in experimental 
plots at Grignon showed a marked increase of 
soil nitrogen, which was no doubt due to a great 
extent to the presence of the innumerable roota 
that fill the soil and take uj) the nitrogen as 
fast as it becomes available: but we do know 
from wh!;t other catises, since we cannot see into 
nature's dark laboratory. 
It is stated that IfiO lbs. of nitrogen that is 
put into the soil by legumes is equal to about 
1,000 lbs of nitrate of soda. • 
!Mucli has been written about the properties of 
special plant>», such as the cow-pea as nitrogen 
collectors. No doubt some legumes have an 
advantage over others in this respect, and the 
highly-recommended Florida bean is now to the 
front as one of the best for the purpose, but 
what we would like to see in tropical agricultui« 
is the acknowledgement of the importance of 
green manuring and some beginning made in the 
adoption of practical measures for preserving the 
humus of our soils, for it has been proved beyond 
a doubt that it is in this element of soil that 
the jjermanent fertility of lar.d lies ; and tiiat the 
simple and inexpensive system of growing legumes 
between annual crops and together wirli peren- 
nials, for the purpose of green manuring, 
if adopted as a regular item of cultivation, should 
do much towards the reduction of the cost of 
cultivation and the maintenance of the fertility 
of our soils. 
