172 
Forrest also states definitely that he found rhodo- 
dendrons with their roots actually spreading in 
the crevices of the limestone rock. 
From the evidence of Mr. Forrest and Lady 
Wheeler-Cuffe it would appear that these par- 
ticular rhododendrons must come in contact with 
a large quantity of lime, but, unfortunately, we 
have no definite information as to the particular 
character of the limestone rocks on which they 
have been found. ' 
In the European Alps the two endemic species 
of rhododendron, R. ferruginewm and R. hirsutum, 
are recognised as being chalk-avoiding and challx- 
loving respectively. R. ferrugineum is found in 
damp, deep-layered soil rich in humus, and it 
will only grow in a limestone region when 
there is an overlying layer of humus. R. 
hirsutum, on the other hand, is a limestone 
rock plant, found in dry, open situations, 
and when the two species are found in the 
same locality, R. hirsutum grows only on the 
rocks, while R. ferrugineum occurs in the pockets 
of humus. The hybrids which have been raised 
in gardens with R. hirsutum as one of the parents 
are also lime-loving, like that species. 
Several of the new Chinese rhododendrons 
which were collected on limestone are now being 
experimentally cultivated in this country on 
various lime-containing soils. Some of the species 
(see Grove in Gardeners’ Chronicle, January 209, 
1916, p. 65) appear to thrive under these condi- 
tions very well, while to others the lime has 
proved fatal, but the experiments have not been 
in progress for a sufficiently long time for a 
definite verdict as to the behaviour of these lime- 
stone rhododendrons under cultivation to be given. 
The abhorrence of lime by the humus-loving 
rhododendrons appears to be intimately connected 
with the mycorrhiza, the symbiotic fungus which 
lives in association with the roots of the rhodo- 
dendron and heath family (Ericacez), and performs 
the functions of the root-hairs in absorbing water 
from the soil; and it may be that the mycorrhizal 
fungi associated with the humus-loving forms of 
rhododendron are physiologically, if not specifi- 
cally, distinct from those of the lime-loving 
species. 
It has recently been shown by Rayner, Jones, 
and Tayleur (New Phytologist, vol. x., 1911, 
pp- 227-240) that the common ling, Calluna vul- 
garis, though it is sometimes found on chalk 
downs, is really growing in pockets of loamy 
soil rich in mineral constituents but poor in lime. 
It is also worthy of note that in the “limestone 
pavement”’ district of Westmorland ling grows 
vigorously in the very thin layers of earth which 
lie directly on the limestone rock. An analysis 
of the surface soil, however, reveals an almost 
complete absence of lime, and so lime-free is this 
" layer that it is actually necessary to add lime 
thereto in the course of ordinary agricultural 
operations. 
Cultures made by C. A, Weber and Graebner 
(see Graebner, “Lehrbuch der Allgemeinen 
Pflanzenphysiographie,”’ 1910, p. 236) have shown 
that the lime-avoiding Ericacee and other plants 
NO. 2453, VOL. 98| 
NATURE 
[NovEMBER 2, 1916 
they examined suffer from lime only when this is 
associated with a large amount of soluble salts, and 
that root-formation fails when nutritive salts are 
in abundance in the presenee of lime. Rhodo- 
dendrons, however, do not appear to have been 
among the plants examined. f 
In connection with their behaviour towards 
lime-containing soils, plants may be roughly 
divided into two groups: of those which avoid 
lime, the heath family affords one of the most 
striking examples, but, contrary to expectation, 
certain members of the family, as, for instance, 
R. hirsutum, are characteristic plants of lime- 
stone districts. 
It seems probable from the evidence now before 
us that some of Forrest’s newly discovered Chinese 
rhododendrons, as also the one found by Lady 
Wheeler-Cuffe, must be reckoned as lime-loving 
species, but in all these cases the interesting 
question as to the quantity of lime absorbed by 
the plants growing on limestone rock still awaits 
an answer. Under natural conditions these lime- 
loving rhododendrons are flourishing on what we 
should consider a very sterile medium, and it may 
be that the poor growth which such plants exhibit 
when grown in lime-containing soil in our gardens 
is due to the superabundance of soluble nutritive 
salts, which may cause the lime to react unfavour- 
ably on the mycorrhiza of the roots, and that, © 
under certain chemical conditions, the lime may 
have a definitely toxic influence. A. W. H. 
NOTES. 
Ar a meeting of the council of the National Museum 
of Wales held at Cardiff on October 28, it was 
announced that’ a sum of 10,0001. had been received 
in War Loan Scrip from Capt. W. R. Smith, senior 
partner of the firm of W. R. Smith and Son, Cardiff, 
and Mrs. Smith towards the building fund of the new 
museum. The generous donors had made this gift 
in the belief that the National Museum would be one 
of the first educational influences in the Principality. 
There were other donors, who wished to remain 
anonymous for the present, and it is expected that 
when the present contract has been paid there will 
be a balance of about 16,0001. towards the 50,0001. 
which is needed to complete the furnishing and equip- 
ment of the portion of the building at present in course 
of erection. 
DEALING with the fine collection of statues of 
eminent Welshmen at Cardiff unveiled by Mr, Lloyd 
George, a correspondent, writing in the Western Mail, 
points out with regret that no man of science figures 
in the series. He says that Robert Record, of Tenby, 
who flourished in the first half of the sixteenth century, 
might well have been included. Record was a man of 
cyclopeedic knowledge, and was most eminent in his 
time, though little known to modern Welshmen. The 
use of the sign = to denote equality was introduced 
by him in 1557. He was “the first mathematician 
who wrote on arithmetic in English; the first who 
wrote on geometry in English; the first who introduced 
algebra into England; the first who wrote on astro- 
nomy and the doctrine of the sphere in English; and, 
finally, the first Briton (in all probability) who adopted 
the system of Copernicus." As a statue or two are 
still to be added, perhaps science may yet be repre- 
sented in the Welsh Valhalla. 
