INTRODUCTION TO CRYPTOGAMIC BOTANY. 549 



whence there are specimens in Hook. Herb., and from no part 

 of Asia north of the Himalayas. Helminthostachys is similar 

 to Botrychium in habit, and has whorls of sporangia which 

 open vertically, surmounted by a crested appendage. It is a 

 native of Ceylou. BotrychiuTn virginicum is used as a pot- 

 herb in New Zealand, as is Helminthostachys in the Moluccas, 

 and the Adder's tongue in some parts of Europe. They are 

 considered as vulneraries, and for that purpose the fronds are 

 boiled in fresh lard. Their virtues are probably only imaginary. 

 Adder's tongue ointment has been much used within my own 

 knowledge for dressing open wounds. The roots are often 

 thick and bulblike, and a new plant comes up every year from 

 the same root, as in terrestrial Orchideae. Sheep are so fond 

 of B. lunaria that it is difficult to get specimens where they 

 have access. These plants are plainly connected with Club- 

 mosses by Rhizoglossum, a Cape genus which has pre- 

 cisely the habit of Phylloglossum (Fig. 118), consisting of a 

 few subulate leaves and a pedunculate spike of sporangia. 

 Ophioglossum varies almost infinitely in size, and in the 

 greater or less elongation of the frond. 



III. EQTJISETACE.S;, D. G. 



Stems branched, articulated, hollow ; branches whorled, 

 destitute of anything in the shape of leaves, except the fimbri- 

 ated sheaths which surround the base of each articulation. 

 Sporangia dependent from the peltate scales of little strobili. 

 Spores surrounded by a membrane splitting spirally into two 

 bands, attached by their centre, and clavate at either end. 

 Archegonia and spermatogonia on the prothallus. 



625. The peculiar habit of these plants, resembling that of 

 Ephedra and Gasuarina, at once distinguishes them from all 

 other Cryptogams. They are commonly known by the name 

 of Horsetails, and are amongst our commonest weeds in 

 ploughed fields and marshy spots, in woods, or on the banks 

 of rivers, and sometimes they are found in loose sand, which 

 they tend to bind together by their delicate rootlets. 



626. The spores germinate like those of ferns, and produce 

 a prothallus which differs only in its irregular fasciculate aspect 



