Minnesota Plant Life. 



163 



roots into the soil and begins an independent life. The spore- 

 producing plants like those of cliib-mosses are perennial, but 

 the egg- and sperm-producing plants die within a few weeks or 

 months after they are formed. 



Quillworts. A very curious group of plants known as quill- 

 worts, found growing on lake bottoms in northern Minnesota, 

 are considered to be distant relatives of the adder's-tongue ferns. 

 They produce two sizes of spores, large and small, and quite as 

 in the life-history of the smaller club-mosses the large-spores 

 give rise to internally developed females, while the small-spores 

 produce diminutive males 

 not protruded beyond the 

 spore walls. E m b r y o 

 quillwort plants originate 

 from the fecundated eggs 

 and when they have be- 

 come old enough renew 

 the production of spores. 

 These are formed in cu- 

 riously partitioned cham- 

 bers at the base of. and on 

 the inner face of the long 

 quill-shaped leaves. The 

 spore-producing area of 

 the leaf occupies the same 

 relative position w-ith ref- 

 erence to the starch-mak- 

 ing area that was seen in 

 club-mosses and adder's- 

 tongue ferns. The upper portions of the leaves contain air- 

 chambers by means of which the leaves stand erect at the bot- 

 tom of the lake. Some varieties of quillworts, also represented 

 in Minnesota, grow in swamps and marshes and cannot be dis- 

 tinguished except by the closest observation from tufts of sedge 

 or grass. 



Ordinary ferns. Quite different in a number of structural 

 details are the "true" ferns, the group to which almost nine- 

 tenths of the Minnesota species belong. These are plants with 

 habits of growth which are, in a general way, pretty well known 



Fig. 53. 



Virginia grape-fern. 

 Brown. 



After Britton and 



