On the Multiplication of Vegetable Cells by Division. 441 
forward in the preceding pages to the investigations of other in- 
quirers. 
In the first place, with regard to the action of sulphuric acid 
and iodine upon the various membranes, H. von Mohl* * * § has shown 
that this depends more upon the age of the structure than any- 
thing else. He finds that these reagents produce the blue colour 
in young cell-membrane, and that the older structures which are 
usually coloured brown, are brought into a condition to acquire 
the blue tint with iodine by boiling in nitric acid or solution of 
potash ; and this without destroying the membrane, at all events 
without converting it into starch, since it remains insoluble in 
boiling water. He finds solution of potash produce the effect 
best in epidermal structures ; nitric acid in the ligneous tissues. 
It is uncertain whether this altered condition of old tissues de- 
pends on spontaneous alteration or the penetration of the tissue 
by new substances. Unger f also states that these structures 
which are usually coloured brown by iodine may be made to ac- 
quire the blue colour by boiling in concentrated sulphuric acid. 
These observations show that mere chemieal reaction is not suffi- 
cient to determine the physiological nature of the tissue. The 
outer layer, which Prof. Mitscherlich calls the cuticula^ is appa- 
rently the wall of the original cell ; the new eeli-walls do not form 
part of it, being deposited on its interior in successive layers, with 
which the new septa are continuous. 
With regard to the process of division many modifications of 
opinion exist ; almost all recent observers however agree in attri- 
buting the prineipal influence to the substance which Prof. Mit- 
scherlich calls the gelatinous mass. This is the Schleim of most 
German authors, translated by many English authors as mucus, and 
by myself always as mucilage or mucilaginous matter ; a bad term, 
and one which it would be desirable to replace universally by the 
one proposed by H. von Mohl, Protoplasm, which involves no 
theory of its chemical nature, but certainly is correct in the view 
it assumes of the function of this matter. Some German authors 
apply the general term of Inhalt or cell-contents to it : it is the 
cytoblastema of Schleiden and the endochrome of other authors. 
KutzingJ holds that this protoplasm is enveloped in a speeial 
membrane, whieh he calls the amylid-zelle. H. von Mohl§ de- 
* Ueber das Waclisilium der Zelhnenibran. Bot. Zeitung, vol. iv. p.3.37, 
1846. — Translated in Annals of Nat. Hist. Ser. 1. vol. xviii. p. 145, 1846. 
Untersucbung der Frage: Bildet die Cellulose die Grundlage sainmtlicher 
vegetabilischen Membran ? Bot. Zeitung, vol. v. pp. 497, 521, 54.5, 1847. 
t Die Intercellularsubstanz und ibr Verbaltniss zur Zellmembran bei 
Pflanzen. Botanische Zeitung, vol. v. p. 289, 1847. 
.■j; Linnaea, 1841, p. 546. 
§ Beitrage zur EnUvickelungsgescbichte der Pflanzen. Botanische Zeit- 
ung, vol. i. 1816. — Translated in Taylor’s Scientific Memoirs, vol. iv. p. 91. 
