OTHER FERN -LIKE PLANTS 351 



sometimes broader than its length. The leaves are thus borne 

 in tufts. The roots extend from the lower part of the broad 

 stem (fig. 339). There are two kinds of spores, large and small, 

 and both kinds of gamete plants lack chlorophyll. The quill- 

 worts resemble certain grasses in the form of the narrow part of 

 the leaf. 



COMPARATIVE REVIEW OF THE FERN PLANTS.* 



520. Relation of the ferns to the liverworts. Although 

 the ferns are much more highly organized than the liverworts it 

 is believed that they have had their origin from the liverworts, 

 that is, from some liverwort which existed ages ago 'but which 

 is now extinct. Of those now existing the horned liverworts 

 (Anthoceros) come nearest this supposed ancestor of the ferns. 

 The adder's tongue fern (Ophioglossuni), which is a member of 

 the class to which the true ferns belong (Class Filicinea], is one 

 of the lowest ferns and its sporophyte has some points of resem- 

 blance to that of Anthoceros. In the adder's tongue fern there is 

 a simple slender stalk, in the upper end of which the spore cases 

 are imbedded and separated by sterile tissue.f ' On this stalk 

 there is a simple blade, the leaf. This is, of course, far from 

 being the equivalent of the sporogonium of Anthoceros but is 

 more like it than is the sporophyte of any other of the fern plants. 

 It suggests, however, that it may have been derived from some 

 Anthoceros-\ike ancestor. Other members of the order (Ophio- 

 glossales) to which the adder's tongue belong have divided leaves, 

 and members of still other orders which cannot be described 

 here lead up to the condition of our common ferns, from massive 

 and simple sporangia to the specialized sporangium which has 

 been described for the common ferns. From the true ferns 



* For reference. 



t The roots of the adder's tongue and of other members of the order 

 (Ophio gloss ales) to which it belongs are fleshy and have a fungus in their 

 tissues, thus forming a mycorhiza (see paragraph 205). The prothallium of 

 the members of the order is a degenerate, tuberous structure, devoid of 

 chlorophyll and also associated with a fungus. 



