258 



THIRD GROUP. — VASCULAR CRYPTOGAMS. 



the spermatozoids (spermatocytes) are formed by division of a central cell of the 

 young antheridium. 



The archegonia are formed from single superficial cells of the meristematic 

 anterior margin of the fleshy lobes of the female prothallium ; as the thallus beneath 

 them continues to grow, they come, as in Pellia, to be on its upper surface. The 

 direction of the archegonium is therefore the opposite to that of the homosporous 

 Ferns ; the neck points upwards ; but the development agrees perfectly with that of 

 the archegonium in the Filicineae, except that the neck-canal-cell does not extend 



I'IG. 210. A male prothallium with the first antheridia 

 a a{ Equisetutn arveitse, after Hofmeister. .ff— ^spermato- 

 zoids of Eqiiisetum Telmateja, after Schacht. A magn. 



Fig. 211. Vertical section of a lobe of a strong 

 female prothallium of Equisetiim arveiise ; at a, a, a 

 two abortive and one fertile archegonium, A rhizoids. 

 Magn. about 6oo times. 



the whole length of the neck. The four long upper cells of the neck bend radially 

 outwards in a half circle, like a four- armed anchor, when the canal opens. 



Development of the asexual generation {sporophore, sporophyle) which forms the 

 spores. The succession of the divisions and the formation of the organs in the 

 embryo is the same, according to Sadebeck, as in the Filicineae. The first wall, the 

 basal wall, is nearly transverse to the axis of the archegonium; then follows the 

 division into octants by the formation of the transversal and median walls at right 

 angles to the basal wall. Of the four quadrants in the upper or epibasal half, one 



