10 OUR NATIVE FERNS AND THEIR ALLIES. 



25. Venation. The method of veining admits of great 

 variation, often serving to distinguish species, and more especi- 

 ally the sections of the various genera. In some ferns, like most 

 shield-ferns (Aspidium),\h& veins are free that is, arising from 

 either side of the midvein they do not unite with any other vein. 

 In some of these the vein is simple (not branched), in others 

 variously forked. In many the veins repeatedly anastomose 

 or unite together, forming a series of network or areolcz. This 

 may be somewhat irregular, as in Onoclea / or forming a single 

 row of areolae next to the midvein and thence free to the margin, 

 as in Woodivardia Virginica ; or forming many uniform areolae 

 by the parallel transverse veinlets connecting the distinct and 

 parallel primary veins, as in PolyJ)odium phyllttidis. In case 

 the venation does not appear when examined by reflected light, 

 it may be brought out clearly by holding the frond between the 

 observer and the light, and then using a lens if necessary. A 

 few fleshy species require dissection to show the veins. 



CHAPTER III. 

 FRUCTIFICATION IN FERNS. 



" But on St. John's mysterious night, 



Sacred to many a wizard spell, 

 The hour when first to human sight 

 Confest, the mystic fern -seed fell." 



26. Spores and Sporangia. In the flowering plants 



(SPERMAPHYTA) there is a 

 manifest sexual reproduction, 

 the ovules in the female organs 

 (pistils) being fertilized by the 

 pollen produced by the stamens, 



thus giving rise to the embryo 



FIG. i. Enlarged section through a * 



sorus of Polypodium falcatum Kellogg, of the new plant. The FemS, 

 showing the stalked sporangia. , 



on the contrary, produce no 



flowers. Instead of seeds developed from fertilized ovules, 

 minute spores are produced asexually, from which new ferns are 

 developed by a peculiar process of germination very unlike that 



