22 
Scott and Brebner . — On the Secondary 
assumed that these structures are tracheides, each arising by 
the growth of a single cell, without any fusion of cells taking 
place 1 . But the first who endeavoured to establish this 
opinion on a firm basis was Krabbe, in his remarkable work 
on sliding-growth 2 . Although he states that he directly 
observed the young tracheides in process of elongation, he 
relies chiefly on the comparison of transverse sections, and on 
careful counting of the various elements of the secondary 
bundle at different stages of development. He established 
accurately the exact amount of growth in length of each cell 
which must take place ; in Dracaena Draco , for example, he 
showed that the mature tracheide is, on the average, no less 
than thirty-eight times as long as the ‘ procambial 3 ’ cell from 
which it developes. As, in this case, the average number of 
tracheides in the transverse section of a mature bundle happens 
to be also thirty-eight, the striking conclusion follows, that as 
a rule the entire system of tracheides of each bundle arises 
from a single series of cells, so far as this species is concerned. 
The predominant share taken by sliding-growth in all such 
cases of tissue-development, is obvious. 
A totally different account of the development was however 
given, almost simultaneously with Krabbe’s work, by Kny 4 . 
1 See, for example, De Bary, Vergleichende Anatomie der Phanerogamen u. 
Fame, 1877, p. 638, English Edition, p. 620: Strasburger, Das botanische 
Practicum, 1st edit. 1884, p. 127. 
2 Krabbe, Das gleitende Wachsthum bei der Gewebebildung der Gefasspflanzen, 
Berlin, 1886. Reviewed in Annals of Botany, vol. ii. p. 127. 
3 The word procambium , introduced by Sachs (see his Text-book, 2nd 
English ed. p. no), means the strand of primary meristem from which a vascular 
bundle arises. Its name implies that it is a structure prior to the cambium, in 
cases where the latter is present. Hence procambium appears a very inappropiate 
name for a tissue which is itself produced from a secondary meristem, 
as is the case with the young bundles formed from the cambium in Dracaena , &c. 
The term desmogen, however (used by Russow as synonymous with procambium, 
see his Vergl. Untersuchungen, 1872, p. 178) may we think well be applied here. 
We propose to speak then of secondary desmogen to indicate the strand of young 
tissue from which a secondary bundle developes, in the Monocotyledons under 
consideration. 
4 Botanische Wandtafeln, Text, VII, 1886, and Beitrag z. Entwickelungs- 
geschichte der * Tracheiden,’ Berichte d. deutsch. bot. Gesellschaft, Bd. IV . 
p. 267, 1886. The former appeared just before, the latter just after, Krabbe’s 
publication. 
