Minnesota Plant Life. 



of which a tuft of delicate threads protrudes. As the frothy 

 masses in which the small-spores are imbedded drift near one 

 of the large-spores, 

 their anchors be- 

 come entangled i n 

 the hairs of the large- 

 spore, and thus one 

 or more of the mass- 

 es is secured in such 

 a position that when 

 the small-spores 

 germinate, protrud- 

 ing from each a 



little tubular Olailt- ^ IG - 62. Portion of maiden-hair fern-leaf, showing marginal 



pockets, which serve to protect the clusters of spore -cases 

 bOCly, the SpermS, under each flap. After Atkinson. 



formed by the male, 



will not have far to swim to reach the egg. 



Explanation of what fern 

 leaves really are. In all the 

 ferns belonging to the series 

 known as the true ferns, the 

 spore-cases are little stalked pods 

 containing from one to about 

 sixty four spores, never much ex- 

 ceeding that number. These 

 spore-cases may be seen in the 

 polypody, forming on the under 

 side of the leaves small brown 

 circular patches. In the maiden- 

 hair and bracken-ferns they oc- 

 cur under pocket-shaped flaps of 

 the leaf-margin. In the shield- 

 ferns each group of spore-cases 

 on the under side of the leaf is 

 protected, at least while young, 

 by a shield-shaped or umbrella- 

 shaped membrane growing over 

 the group. It is the rule among 



the true ferns that the leaf which bears the spore-cases also 



serves as the starch-making organ of the plant, but in the OS- 



FIG. 63. A patch of spore-cases on the back 

 of a common polypody-fern-leaf. Mag- 

 nified. After Atkinson. 



