MICROSCOPIC STRDCTURE OF HIGHER CRXTTOGAMIA. 



347 



to form a kind of confervoid filament (c) ; but the multiplication of cells 

 by subdivision soon takes place transversely as well as longitudinally, so 

 that a flattened leaf-like expansion (D) is produced, so closely resembling 

 that of a young Mar chant ia as to be readily mistaken for it. This expan- 

 sion, which is termed the pro- 

 thallium varies in its configura- , FIG.. 232. 

 tion, in different species; but its 

 -essential structure always remains 

 the same. From its under sur- 

 face are developed not merely the 

 root-fibres (a, b) which serve at 

 the same time to fix it in the soil 

 and to supply it with moisture, 

 but also the antheridia and arch- 

 ggonia which constitute the true 



representatives of the essential Development of the Antheridia and Antherozoids 

 r>flrf<3 nf thp THmvpr nf Viicrhpr of Pt eris serrulata: A, projection of one of the 



mgnei cells of prothallium, showing the antheridial cell 6, 

 Plants. Some Of the former may with its sperm-cells e, within the cavity of the origi- 



be distinguished at an early period ^^^iS^^l^^SSSSSS^S^. 

 of the development of the Hx>tM^ 



/? TA J T-7 & magnified, showing its large extremity o, its 



lium (fly /I) ; and at the time Of its small extremity b, and its cilia d, d. 



complete evolution these bodies ^ -^ 



are seen in considerable numbers, A 



especially about the origins of the 

 root-fibres. Each has its origin 

 in a peculiar protrusion that takes 

 place from one of the cells of the 

 prothallium (Fig. 232, A, a): this 

 is at first entirely filled with chlor- 

 ophyll-granules; but soon a pecu- 

 liar free cell (b) is seen in its in- 

 terior, filled with mucilage and 

 colorless granules. This cell 

 gradually becomes filled with an- 

 other brood Of yoUUff Cells (e}, Archegonium otPteris serrulata: A, as seen from 



\- ; above; a, a, a, cells surrounding the base of the cav- 



mcreases Considerably in ltSity;&, c, d; successive layers of -cells, the highest in- 

 '.OnS. SO as to fill the pro- closing a quadrangular orifice : B, side view, show- 

 ,.' i . , .. .1 . . mg A, A. cavity containing the germ-cell, a; B, B, 



JCCtlOn Which incloses it: this part walls of the archegonium, made up of the four lay- 



, thp nrifriml PflX'itv i<5 now Pn f ere of cells, 6, c, d, , and' having ~an opening,/, on 

 )llglliai Ca\lty L u the summit :c,c, antherozoids within the cavity; g< 



Off from that of the Cell Of Which large extremity; h, thread-like portion; t, small 

 it was an offshoot, and the an ther . extremity in contact with the germ-cell and dilated. 



idium henceforth ranks as a distinct and independent organ. Each of the 

 sperm-cells (B, e) included within the antheridial cell, is seen, as it 

 approaches maturity, to contain a spirally-coiled filament; and when set 

 free by the bursting of the antheridium, the sperm-cells themselves burst, 

 and give exit to their antherozoids (c), which execute rapid movements 

 of rotation on their axes, partly dependent on the six long cilia with 

 which they are furnished. 



343. The archegonia are fewer in number, and are found upon a 

 different part of the prothallium. Each of them originates in a sin- 

 gle cell of its superficial layer, which undergoes subdivision by a horizon- 

 tal partition. Of the two "cells thus produced, the upper gives origin, 

 by successive subdivisions, to the ' neck ' of the archegonium, which, 

 when fully developed (Fig. 233), is composed of twelve or more cells, 



