THE GENUS K(iUISKTUM. 



L69 



cells of which have been outlined with the camera lucida, a is the apical <'<'ll and /• is the 

 rudiment of the root. It might be thought that another cell, further down on the right of 

 the young embryo, is really the radical rudiment, but that such is not the case may he 

 determined from the next figure, which is a hawing of an older embryo made with the 

 camera, Lucida. The upwardly directed arrows in the two last mentioned figures indicate 

 the direction of the nock of the archegonium, and those pointing downwards, the position 

 of the embryos in relation to the substratum, as inferred from the course of the prothallial 

 root-hairs. It will be seen from these figures, that the root appears very early in K. 

 hiemale, and in all probability is derived from the epibasal region of the embryo. It [(re- 

 sents in the latter feature a close correspondence to the state of affairs observed by Treub 

 (op. cit.) and Bruchmann (op. cit.) in the embryos of Lycopodium cemuum, L.phlegmaria, 

 L. clavatwn, and L. complanatum. The segmentations of the apical cell become numer- 

 ous before the first whorl of leaves makes its appearance in embryos of nearly twice 

 the size of that of Fig. 8. It is accordingly not easy to trace the members of the first 

 foliar whorl to the epibasal octants by allo*wing, as is usually done, one for the apical cell, 

 and one for each of the three primary leaves. It would seem to be a more reasonable 

 procedure to compare the embryo of Equisetum rather with those of the Lycopodiales, 

 concerning which we have in recent years so much information, which was entirely lacking 

 when the fashion of comparing all embryos with those of the probably highly specialized 

 leptosporangiate ferns originated. Such a comparison would lead to our deriving both 

 root and shoot from the epibasal half of the embryo, and leaving the whole hypobasal por- 

 tion for the foot. Without, however, attaching too^ much importance to this comparison, it 

 may be safely stated that the primitive root of E. hiemale originates high up on the side 

 of the embryo and in close relation to the primitive shoot. As the embryo develops, the 

 root gradually descends, and finally as it begins to push its way' out, becomes the most 

 inferior organ of the embryo. The young root is directed towards the apex of the game- 

 tophyte and alternates with the two anterior leaves of the first foliar whorl. The first so- 

 called adventitious bud originates above the point of origin of the first root, and likewise 

 between the two primary leaf-traces. The secondary axis differs from the primary in not 

 producing the rudiment of the root, till the first foliar whorl is clearly indicated, as a fold 

 round the secondary stem-apex. About the time of the appearance of the first adventi- 

 tious bud, and when three or more whorls of leaves have been formed on the young axis, 

 the shoot breaks through the calyptra, the root having previously in the case of E. 

 hie male and E. arvense made its way into the soil. In E. limosum the root develops very 

 slowly and does not enter the soil till long after the shoot has made its way out. This is 

 probably the result of its amphibious mode of life, as many plants of this habit have a 

 poorly developed primary root e. g., Nehnnhtum luteum. The writer has not a sufficiently 



