SECT. I 



CRYPTOGAMS 



443 



Club Mosses, and represent the most highly developed Cryptogams. In 

 the development of the plants forming this group, as in the Bryophyta, 

 a distinct alternation of 

 generations 



is exhibited. 

 The first generation, the 

 sexual, bears the anther- 

 idia and archegonia ; the 

 second, the asexual, de- 

 velops from the fertilised 

 egg and produces asexual, 

 unicellular spores. On 

 germination the spores in 

 turn give rise to a sexual 

 generation. 



The haploid SEXUAL 

 GENERATION is termed the 



PROTHALLIUM or GAMETO- 



PHYTE. It never reaches 

 any great size, being at 

 most a few centimetres 



in diameter ; in some 



Fig. SSS.—Aspidium filix rtias. A, Prothallium seen from 

 below ; or, archegonia ; an, antheridia ; rh, rliizoids ; B, 

 prothallium with young Fern attached to it by its foot; 

 ?<, the first leaf ; wi, the primary root, (x circa 8.) 



forms it resembles in ap- 

 pearance a simple, thalloid Liverwort ; it then consists of a small green 

 thallus, attached to the soil by rhizoids springing from the under side 



(Fig. 388,^). At other 

 times the prothallium 

 is branched and fila- 

 mentous ; sometimes it 

 is a tuberous, colourless 

 mass of tissue, partially 

 or wholly buried in the 

 ground, and leading a 

 saprophytic existence, 

 while in certain other 

 divisions of the Pteri- 

 dophyta it undergoes 

 reduction and remains 



Fio. 3S9.— J, P/e/(Sser)-((tafa, embrj'O freed from the archegonium, niore Or IcsS Completely 

 in longitudinal section (after Kienitz-Gerloff) : I, basal wall ; „,, „1„„„^1 u/ifViin tVip 



//, transverse wall dividing the egg-cell into quadi-ants ; rudi- 

 ment of ths foot/, of the stem s, of the first leaf '/, of the root 

 iy; B, section of a further-developed embryo of i'/cris aquilina 



(after Hofmeister) ; /, foot still embedded in 

 venter of the archegoniuin aw ; pr, prothallium. 



the enlarged 

 (Magnified.) 



spore. On the pro- 

 thallia arise the sexual 

 organs, antheridia 

 (Figs. 393, 400), pro- 

 ducing numerous ciliate, usually spiral spermatozoids, and archegonia 

 (Figs. 394, 401), in each or which is a single egg-cell. As in the 

 Mosses the presence of water is necessary for fertilisation. The 



