24 Scott and Brebner.—On the Secondary 
If this be true, we ought to find, on macerating a young 
bundle, tracheides at all stages of elongation, and each of 
them would probably contain a single nucleus only. Roseler 
succeeded in demonstrating that these conditions are realized. 
He figures young thin-walled tracheides, isolated by macera- 
tion, measuring 0-4 mm., 0-84 mm., and i«8 mm. in length, 
i. e. about four times, eight times, and eighteen times respec- 
tively, the length of the original desmogen-cell. Each con- 
tained a single conspicuous nucleus 1 . These observations 
were in reality decisive, but the effect of Roseler’s work was 
somewhat enfeebled by the weakness of some of his other 
arguments. Thus his elaborate countings of the elements in 
transverse sections led to no definite result, but might seem 
rather to favour a mixed origin, by cell-fusion with subsequent 
elongation 2 . He also failed to obtain any satisfactory evidence 
from longitudinal sections, in consequence of manipulative 
difficulties 3 In spite, therefore, of the great merits of his 
paper, we cannot wonder that it failed to settle the question. 
Roseler’s work was reviewed by Wieler, in the Botanische 
Zeitung 4 , with great and indeed unjustifiable severity. Wieler, 
however, contributed nothing himself to the decision of the 
points in dispute. 
In 1891 Strasburger published his great work on the 
vascular tissues, and in this he withdraws his former view, 
and declares in favour of the origin of the tracheides by direct 
elongation of the short cells derived from the cambium 5 . 
He directly observed the young tracheides in sections, and 
confirms Roseler’s statement that they are uninucleate. The 
observations of Roseler and Strasburger established a strong 
presumption that the view of Krabbe was, after all, the right 
one. A re-investigation, however, seemed to us desirable, 
especially as the observations previously made by one of us 
had seemed to favour the opposite conclusion. We attached 
1 1. c. p. 339. 2 l. c. p. 333. 3 l. c. p. 334-338- 
4 Bd. 47, 1889, p. 701. 
5 Strasburger, Ub. den Ban u. die Verrichtungen der Leitungsbahnen in den 
Pflanzen ; Histologische Beitrage, III, 1891, p. 400. 
