and Histogeny of Strychnos. 277 
in the wood. They form, together with thin-walled paren- 
chyma, isolated strands surrounded on all sides by the tissues 
of the xylem. According to de Bary ‘ suitable develop- 
mental stages easily show that these phloem-strands in the 
wood are given off by the cambial zone towards the inside V 
It should be noted that de Bary had no fresh material of the 
stem more than 1 mm. in thickness. All his observations 
relating to the anomalous secondary growth were made on 
dry material. His Fig. 229, the only one given, is a diagram- 
matic, slightly magnified transverse section, and throws no 
real light on the development. A similar structure is de- 
scribed in the malpighiaceous genus Dicella , which was also 
one of the plants observed by Fritz Muller. 
In another passage 2 de Bary draws a comparison between 
the structure of Strychnos and that of certain Chenopodiaceae, 
and formulates a general rule, applicable to all such cases, 
that all secondary tissue formed centrifugally inside the 
cambium is to be regarded as wood, while all that is formed 
centripetally on its outer side belongs to the bast. On this 
principle the secondary phloem-strands of Strychnos come 
under the category of wood. With one exception, to be 
mentioned immediately, all later writers on the subject seem 
to have simply adopted de Bary’s statements as to this 
genus 3 . We shall see later on that the anatomical peculiarity 
consisting in the presence of phloem groups imbedded in the 
xylem is now known to occur in many genera besides the two 
mentioned by Fritz Muller and de Bary. 
Herail’s Recherches snr V anatomie comparee de la tige des 
Dicotyledones 4 contain a valuable series of observations on 
the development of anomalous stems, and Strychnos is among 
the genera investigated. His account of the development is 
much the most satisfactory which we possess, His chief re- 
sults are as follows : he finds, in agreement with de Bary, 
1 k c - P- 579- 2 1. c. p. 591. 
3 See for example Van Tieghem, Traite de Botanique, p. 796 ; and Solereder, 
Uber den systematischen Werth d. Holzstrnctur b. d. Dicotyledonen, 1885, 
p. 178. 
4 Annales des Sciences Naturelles, ser. vii, T. ii, 1885. 
