
No. 461.] AFFINITIES OF EQUISETUM. 275 
The first view has been strongly advocated by Scott! in 
England, who bases his conclusions upon a study of the fossil 
forms. In America, Jeffrey? has brought forward arguments in 
favor of the same view, from a study of both the gametophyte 
and sporophyte. He goes so far, indeed, as to propose a special 
division of the pteridophytes into the Lycopsida, and Pterop- 
sida, the former including both Equisetales and lycopods, the 
latter the ferns. 
As he has presented his arguments in very clear form, it may 
be well to consider them somewhat in detail, to see how they 
will stand the test of closer examination. 
From a study of the gametophyte of Equisetum,? Jeffrey 
concludes that it most nearly resembles the gametophytes of 
such species of Lycopodium as Lycopodium cernuum or Lycopo- 
dium inundatum. “There are in both cases, the upright fleshy 
axis, and the same characteristically numerous lateral lobes. The 
archegonia of Equisetum and Lycopodium are, moreover, alike, 
in that in both genera they are uniformly without the basal cell, 
which is found without exception in the archegonia of all the 
isosporous Filicales” (/oc. cit., p. 186). He finds also that the 
neck canal cell is divided vertically as in Lycopodium phlegmaria, 
instead of transversely as is the case in the ferns. 
Finally, in the embryo of Zguisetum hiemale and Equisetum 
limosum, Jeffrey thinks that all the organs of the young sporo- 
phyte, including the primary root, develop from the upper or 
epibasal half of the embryo, in this respect also, showing a 
resemblance to the Lycopodiales. 
The points in which the adult sporophytes of Equisetum and - 
Lycopodium agree, are the highly developed axis, and small 
leaves ; the development of a strobilus, and the so-called “ clado- 
siphonic ” vascular cylinder, or stele. It is on the basis of these 
resemblances that Jeffrey proposes the establishment of his micro- 
1 Studies in Fossil Botany — as well as many special papers. 
21. The development, structure and affinities of the genus Equisetum. Mem. 
Boston Soc. Nat. Hist., 1899; 2. Structure and development of the stem in the 
Pteridophyta and Gymnosperms. Phil. Trans. Royal Soc., series B, vol. 195, 
1902 
3 Jeffrey, 1, p. 186. 
