392 EQUISETALES 
some curious features have lately been disclosed for the strands entering 
the sporangiophores. In the case of /adaeostachya vera, where the 
sporangiophores in each whorl approximately equal the bracts, and are 
apparently axillary, the strand for each originates immediately above 
the bract-bundle; it does not, however, pass out, but ascends with 
the main bundle of the axis through half the internode: it is then 
sharply reflexed, and drops again to the upper limit of the nodal 
disc, whence it passes outwards to the sporangiophore.! In 
Calamostachys the course seems to be the same, but with the points of 
difference that the sporangiophore-trace drops less than in Palaeostachya, 
in accordance with the position of the sporangiophore, and that Calamo- 
stachys has commonly two bracts to each sporangiophore, the latter 
being inserted in a plane between them. The anatomical condition in 
Stachannularia and Cingudaria is unfortunately unknown: so far as the 
facts are available they indicate that the vascular supply of the sporangio- 
phore is regularly derived from the bracteal node next below. This 
suggests a certain anatomical relation of the sporangiophores to the bracts 
in Calamarians at large; but the details of that relation are variable, 
and they cannot be held to support any general theory of lateral fusion 
of leaf-segments to form the sporangiophores, such as that suggested 
by Lignier in the case of C. Zedlleri. As regards the position of the 
sporangiophore on the internode, the anatomy, so far as known, appears 
to indicate the condition of Calamostachys,. with its sporangiophore 
halfway up the internode, as a central type: and that while Cingularia 
probably shows an exaggeration of this displacement, so that the spor- 
angiophores appear immediately below the bracts of the next upper 
whorl, Padaeostachya is a modification of the Calamostachys type in the 
opposite direction, so that the sporangiophores are axillary in position.? 
* 
EMBRYOLOGY. 
The archegonium of Zguisetum lies with the neck directed upwards. 
The basal wall, which first segments the zygote, appears approximately 
horizontal: the embryo is thereby divided into epibasal and hypobasal 
halves: the shoot arises from the former, the foot from the latter. There 
is some conflict of evidence as to the place of origin of the first root: it 
is referred by Sadebeck to the hypobasal half in Z£. arvense and palustre 
(Fig. 214);? but Jeffrey traces the origin of the root to the epibasal half 
in £. Aiemale, though with some uncertainty; but in any case it arises 
high up on the side of the embryo in that species, and in close relation 
to the primitive shoot. The absence of a suspensor simplifies the 
embryogeny. As in the Lycopodiales, so here also it will be found 
1 Hickling, Zc., p. 375- 2Compare Scott, Progressus, i., pp. 160-161. 
3See Engler and Prantl, Nat. Pflanzenfam., i. 4, p. 520, where the literature is cited. 
Alem. Bost. Soc. of Nat. Hist., vol. v., No. 5, p. 168. 
