3^4 



VASCULAR CRYPTOGAMS. 



ones scarcely elongate at all, and contribute, by their multiplication, like the cells of 

 the prothallium which surround the central cell, to the formation of the wall of the 

 ventral part of the archegonium, which consists of one or two layers. The oosphere 

 is produced in the central cell, the contents of which it gradually displaces. The 

 four upper long cells of the neck curve radially outwards, when the canal of the 

 neck is being formed, like a four-armed anchor \ Immediately after fertilisation 

 the canal of the neck closes, the oosphere, the nucleus of which disappears (and 



Fig. 270. — A male prothallium of EqiUsetian arvense with 

 the first antheridia a (after Hofmeister, x 200) ; B — E anthero- 

 Eoids of E. Telmateia (after Schacht). 



Fig. 271.— Lobe of a highly developed female prothallium of Equisetttm arvense cut through vertically (after Hofmeister, 

 (X about 60) ; a « a two abortive and one fertilised archegonium, h root-hairs. 



which has now become the oospore), enlarges, and the cells of the wall of the 

 ventral part of the archegonium which surrounds them begin rapidly to multiply. 



Development of the Asexual Generation of Equisetum The formation of the 

 embryo from the oospore is the result of divisions, the first of which is inclined to the 

 axis of the archegonium, and is followed, according to Hofmeister, in each of the 

 two cells by a division-wall placed perpendicularly to the first. The embryo appears 



^ Recent investigations are wanting from the point of view taken in Ferns and Rhizocarps. 

 From analogy, however, the existence of a ' canal-cell ' may be inferred here also. 



