26 
F. E. Fritsch 
If any portion of a plant of Plagiopteron fragrans, Griff, Solaria 
micrantha, Peyr, or of a species of Wimmeria be carefully broken 
into two, it will be remarked, that the two fragments still hang 
together by means of a number of thin white threads. If slowly 
drawn apart, it will be found that the two fragments can be 
separated some little distance from one another before the con¬ 
necting threads snap; and the elasticity of the latter is so great, 
that on relaxing the tension the two pieces again resume a position 
of close proximity. This curious feature has naturally not been 
absolutely unobserved by earlier botanists, although incorrectly 
interpreted. Thus Petit-Thouars 1 in 1806 figures these threads in 
the fruit-wall of Salacia Cahjpso, DC, a plant, abounding in them ; 
whilst De Candolle 2 in 1824 remarks: “ Hippocrateae ovatae 
spermodermium et cotyledones intus singulari modo filis innumeris 
tracheiformibus stuposi! quod etiam in Calypsois suae pericarpio 
vidit cl. Petit-Thouars.” Further Griffith 3 in his original 
description of Plagiopteron fragrans remarks, that the plant 
“ abounds with spiral vessels.” 
The material, constituting these threads, differs from ordinary 
latex in being in a semi-solid state; it is insoluble in alcohol, 
whereas it is more or less completely dissolved by ether, benzol or chlo¬ 
roform. In polarised light it is strongly doubly refractive, this property 
being lost temporarily or permanently when heat is applied. The 
threads have the capacity of taking up certain stains very readily, 
although the different genera and species vary considerably in this 
respect. On evaporation of the benzol-solution, a thin greyish- 
white elastic film remains, which burns with the smell characteristic 
of burning rubber. These characters point to the threads consisting 
of a kind of caoutchouc; according to the French investigators it is 
more of the nature of gutta-percha. 1 With regard to the quantity 
of caoutchouc present it is noteworthy that the bark of Eucommxa 
has yielded as much as 5.7 0 / o , 5 whilst Col finds that 50 grm. of the 
bark of Evonymus japonicus yield 5 grm. Many species of 
Hippocrateaceae must be as rich, if not even richer than this. 
The histological elements, in which this caoutchouc is contained, 
are of the nature of laticiferous cells (or coenocytes ?). In a number 
1 Histoire des Yegetaux D’Afrique. ist Part, p. 20. 
2 Prodromus. I., p. 569, foot-note. 
3 Calcutta Journal of Natural History. Vol. IV., p. 246. 
4 cp. Barthelat in Journal de Botanique. Vol. XIV., 1900. nr. 2 ; 
and Col, loc. cit. 
5 Bulletin of Miscellaneous Information, Kew. September 1891. 
