170 



Minnesota Plant Life. 



of which a tuft of cleHcate 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 plant- ^"iG- 62. Portion of maiden-hair fern-leaf, showing marginal 



pockets, which serv-e to protect the chisters of spore-cases 

 body, the sperms, vmder each flap. After Atkin.son. 



formed by the male, 



will not have far to swim to reach the Qgg. 



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- 

 liair 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 voung, 



I'll., ftj. A jjalch of .'^porci.a.-M.^ on tlic back i • i i i 



ofaconimonpoiypody-fern-icaf. Mag- by a shield-shaped or umbrella- 

 nified. After Atkin.son. sliapcd 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- 



