388 



VASCULAR CRYPTOGAMS. 



ts protoplasmic body is converted into the oosphere. After fertilisation the layer 

 3f tissue of the prothallium surrounding the central cell becomes double ; a few 

 granules of chlorophyll arise in it, and the outer cells grow in Marsilea salvatrix 

 [Fig. 291) into long root-hai-rs, which are especially luxuriant when no fertilisation 

 ;akes place. In the case of Marsilea salvatrix the antherozoids collect in large 

 aumbers at the time of impregnation in the funnel above the prothallium, and 

 'orce themselves into the neck of the archegonium\ 



Development of the Asexual Geiieration. The first processes of division by 

 A'hich, in Salvinia, the oospore is transformed, after fertilisation, into the embryo, 

 lave been most accurately described by Pringsheim. The first division is effected 

 3y a wall which separates the posterior piece of the oospore, above which is the 

 Tiouth of the archegonium, from the anterior piece, which is usually larger ; it is 



Fig. if^.— Marsilea salvatrix ; A pt the prothallium projecting^ through the ruptured membrane r of the spore ; si the 

 layers of mucilage which form the funnel, with a number of antherozoids ; B vertical section of a prothallium pt with an 

 archegonium a and oosphere o; C, D, E young embryos, i- apex of the stem, b leaf, -w root, /" foot (B—E after 

 Hanstein). 



perpendicular to the median line of the prothallium and to its basal surface. The 

 interior cell is next divided by a wall nearly at right angles to the previous one. If 

 the angle enclosed by these two walls is bisected by a straight line (Fig. 289, A, c, d), 

 this line represents the axis of growth of the stem ; the posterior piece of the oospore 

 first cut off is the first segment {A, I), the cell cut off by the second wall is the 

 second segment of the apical cell of the stem which now lies in front and below 

 (A, v); in this latter walls are now formed inclined alternately upwards and down- 

 wards, and by this means the two rows of segments are formed out of which the 

 structure of the stem of Salvinia is gradually developed. In Fig. 289 B are shown, 

 at ///, IV, V, and VI, these segment-cells undergoing still further division. No 

 root is developed either at this period or subsequently ; Salvinia is absolutely rootless. 



* For further details see Hanstein, Jahrb. fiir wiss. Bot. vol. IV. 



