6+ 



Division XIII. PTERIDOPHYTA. 

 Ferns and fern-allies. 



Plants with true roots ; the stems and leaves with 

 fibro-vascular strands. The spore of the true ierns (Order 

 Filices), on germinating, produces a small, thalloid body, 



Fig. 44. 1. Transverse section of the stem of a species of Ahoph'ila. L, Fibrovascular 

 bundles of the main woody cylinder; /, accessory bundles, /<, bundles which are 

 passing into the leaves. (From Wcttstein, Handbuch) 2. Transverse section of 

 the bundle of the rhizome of Pol\potUum glaucophyllum Kunze //, \\lem; 

 L, phloem; P/;, proto-xylem ; E, endodermis. (From Engler and PrantI) 



the prothallium (Fig. 45), which is provided with rhizoids 

 and bears both kinds of sexual organs, viz. antheridia 

 and archegonia, on its under side. In the other groups 

 of the pteridophytes the prothallium is generally much 

 reduced, sometimes not emerging from the spore. The 

 spermatozoids (Fig. 46) swarm in water until they reach 

 the mouth of the archegonium, being attracted thither by 

 traces of malic or citric acid, as the case may be, secreted 

 by the female organ. 



The fertilised oosphere develops into a minute 

 embryo, from which originates the asexual generation (the 

 sporophyte), which is the adult plant. The adult plant 

 produces sporangia (receptacles filled with spores) either 

 directly on the leaves (fronds) or on specially modified 



