filicinem: 



447 





in Sahinia, they form the free neck-portion (which in Marsilia projects only 

 slightly, in Pilularia very much) and the 'closing cells' of the archegonium. Above 

 the central cell, the protoplasm of which contracts, a small canal-cell is visible, 

 according to Hanstein, penetrating between the ' closing cells,' and behaving as 

 in Salvinia. Hanstein was unable to recognise any further cell-formation within 

 the central cell, and he concluded that the whole of its protoplasmic body was 

 converted into the oosphere; Janczewski, however, found here also the ventral 

 canal-cell which occurs in other Vascular Cryp- 

 togams, as a small mass of protoplasm cut off 

 from the central cell. After fertilisation the 

 layer of tissue of the prothallium surrounding 

 the central cell becomes double ; a few chloro- 

 phyll granules arise in it, and the outer cells 

 grow in Marsilia Salvatrix (Fig. 3 1 5) into long 

 root-hairs, which are especially luxuriant when 

 no fertilisation takes place. In the case of 

 Marsilia Salvatrix the antherozoids collect in 

 large numbers at the time of impregnation in 

 the funnel above the prothallium, and force 

 themselves into the neck of the archegonium. 

 Development of the Asexual Generatiojt. 

 The first processes of division by which, in 

 Salvinia, the oospore is transformed, after fer- 

 tilisation, into the embryo, have been most ac- 

 curately described by Pringsheim. l.^he first 

 division is effected by a wall (basal wall) which 

 separates the posterior (hypobasal) half of the 

 oospore, above which is the mouth of the 

 archegonium, from the anterior (epibasal) half, 

 which is usually larger; this wall is nearly per- 

 pendicular to the median line of the prothallium. 

 The two cells are next divided by walls (trans- 

 verse) nearly at right angles to the previous 

 one. If the angle enclosed by these two walls 

 is bisected by a straight line (Fig. 313, A, c, d), 

 this line represents the axis of growth of the 

 stem. This is followed by walls (median) at 

 right angles to the two former, and thus the 

 embryo comes to consist of eight cells, octants 



of a sphere. Of the four epibasal octants, the two upper give rise to the first leaf 

 (cotyledon), which, on account of its peculiar form, is known as the ' scutif(7rm leaf:' 

 one of the two lower gives rise to hairs, and the other to the apical cell of the stem 

 which now lies in front and below (^, v); in this latter walls are now formed 

 inclined alternately upwards and downwards, 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. 313 B are shown, at ///, IV, V, and VI, these segment-cells 



Fig. 315.— Longitudinal section through the spore 

 prothallium and embryo of Marsilia Salvatrix 

 (X about 60) ; atn starch-grains of the spore, i inner 

 coat of the spore burst above into lobes, ex the 

 exospore consisting of prisms, c the cavity beneath 

 the arched diaphragm on which is the basal layer of 

 the prothallium. pt the prothallium, -wh its root-hairs, 

 a the archegonium, f the foot of the embryo, -w its 

 root, s the apex of its stem, b its first leaf by which the 

 prothallium becomes extended, si the mucilaginous 

 epispore which at first forms the funnel above the 

 papilla, and which still envelopes the prothallium fifty 

 hours after the dissemination of the spores. 



