A Contribution to our Knowledge of the Vascular 
System of the Genus Equisetum. 
BY 
KATE BARRATT, M.Sc. 
With Plates VI and VII and twenty-four Figures in the Text. 
I N spite of the large amount of work already published on the subject of 
the anatomy of Equisetum , of which an excellent chronological account 
has been given by Lady Isabel Browne ( 1 ), there still seems to be a con- 
siderable lack of agreement as to the nature and origin of the various parts 
of the vascular system. The presence or absence of centripetal wood is one 
of the most prominent of these questions. As a contribution towards the 
solution of some of these problems it was decided to undertake a more 
thorough investigation of the anatomy of the sporeling, and to bring 
together and amplify our information on the development of the vascular 
system. 
Hofmeister ( 3 ), as long ago as 1852, included a brief reference to this 
subject in his account of the genus. He gave an excellent figure of a young 
sporeling at the stage when its first lateral shoot was developing, but he 
does not refer in detail to the nature of the vascular structure. 
In 1899 Jeffrey ( 4 ) described the development of sporelings of Equi- 
setum hiemale and E. liviosum , but only dealt generally with the anatomy of 
the young plant. 
It was hoped that a further investigation of the sporeling anatomy 
would throw light upon the following points : 
1. The nature of the stelar anatomy of the primary axis. 
2. The phylogeny of the internodal bundle, with special reference to 
the metaxylem. 
3. The elucidation of the vascular system of the node, in relation to the 
internode and the question of secondary thickening. 
Methods. 
One of the reasons for the incompleteness of our knowledge of these 
plants in their young stages probably lies in the fact that the sporelings are 
very slender and fragile, and that previous investigations have been largely 
confined to the examination of microtome sections. 
Although serial sections have been used in this investigation, another 
[Annals of Botany, Vol. XXXIV. No. CXXXIV. April, 1920.] 
