168 EDWARD C. JEFFREY ON 



frequentl}' by sub.se(|ueiit writers. The development of the urchegonium in E. Vimosum 

 and E. arve/itie is practically identical with that of E. hiemale, which has been described 

 above, and they have the same peculiar longitudinally divided cervical canal-cell. Pi. 20, 

 fig. 5 represents a nearly ripe archegoniuni of E. (irueniie. In the two last mentioned 

 S2)ecies the neck is very much longer than in ?]. hiemale and consists of three or four tiers 

 of cells. The luiiforin occurrence of lono-itudinal division in the cervical canal-cell of these 

 three species is interesting and probably indicates tliat this feature will be found to be 

 common to the group. Campbell (Mosses and ferns, p. 427), however, figures a trans- 

 verse division for E.telmateia. Sadebeck (Engler u. Prantl, Nat. pflanzenfam., teil 1, 

 abteil 4, p. 2) has recently published a figure of the archegoniuni of E. arvense which 

 does not at all agree with Fig. 5, but as he does not represent in it the divisions of the pro- 

 thalhal cells parallel to the surface of the egg, and the cuneate insertion of the neck of the 

 archegoniuni which have been noticed by practically all other observers, beginning with 

 Hofmeister, his representation must be regarded as somewhat diagrammatic. 



The first division of the egg is transverse, the basal wall being generally somewhat 

 oblique. The inclination of the basal septum is sometimes towards the apex and some- 

 times towards the base of the prothallus, more frequently, however, towards the former. 

 It has not been possible to absolutely settle the order of the next two divisions, but it is 

 probable that the median wall is formed first. The transverse wall often does not extend 

 at first entirely across the embryo, especially in the hypobasal half. The apical cell is 

 early formed in the epibasal portion, and in the hypobasal half, an apparent apical cell is 

 also differentiated. These features are shown in PI. 20, fig. 0, which is almost identical 

 with Hofmeister's {op. eit., PL 39, fig. 2) illustration of a similar stage. The develop- 

 ment of an apparent apical cell in the lower half of the embryo, and a tacit homologizing 

 of that region with the corresponding region, as regards the substratuna of the leptospor- 

 angiate embryos, with which he was familiar, led him into the error of regarding it as the 

 embryonic primary axis. As its regular segmentations sooii cease, and it is thrust aside by 

 the growth of the upper portion of the embryo, he regarded the primary axis of Equisetum 

 as abortive. Tlie real primary stem-apex in the upper part of the embryo of PI. 1, fig. 0, 

 he regarded as that of a secondary shoot, an error which has been recognized by Sadebeck 

 (Pringsheim's Jahrbiicher, bd. 11, p. 581), and subsequent observers. Sadebeck {oj). cit.) 

 informs us that in the case of E. arvense and E. pahistre, the development of which he 

 has studied, the epibasal cell gives rise immediately to the primitive shoot-axis, from which 

 the first whorl of leaves is derived exactly as are the subsequent ones. This statement I 

 am not aljle to confirm exactly, for in E. hlemaJe, which I have particularly studied, the 

 rudiment of the first root appears very early, next the apical cell, and on the side of it 

 which faces the apex of the prothallus. PI. 20, fig. 7, shows an embryo at this stage, the 



