392 EQUISETALES 



some curious features have lately been disclosed for the strands entering 

 the sporangiophores. In the case of Palaeostachya 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. 1 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 Cingularia 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. Zeilleri. 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, Palaeostachya is a modification of the Calamostachys type in the 

 opposite direction, so that the sporangiophores are axillary in position. 2 



EMBRYOLOGY. 



The archegonium of Equisetum 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 E. arvense and palustre 

 (Fig. 2i4); 3 but Jeffrey traces the origin of the root to the epibasal half 

 in E. hiemale, 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. 4 The absence of a suspensor simplifies the 

 embryogeny. As in the Lycopodiales, so here also it will be found 



1 Hickling, I.e., p. 375. 2 Compare Scott, Progresses, i., pp. 160-161. 



3 See Engler and Prantl, Nat. Pfanzenfam . , i. 4, p. 520, where the literature is cited. 



4 Mem. Bost. Soc. of Nat. Hist., vol. v., No. 5, p. 168. 



