CRYPTOGAMS 



42J 



it produces the bracket-like Lichens of the Dictyonema form, found projecting 

 from the limli.s of trees with a semicircular or nearly circular thallus, having the 

 hynienium on the under side. When the shape of the thallus is determined by the 

 Alga, a Lichen of the Laudatea form occurs as felted patches of tine filaments on 

 the bark of trees, with the hynienium on the parts of the thallus which are turned 

 away from the~light. 



OFFICIAL. The only representative of the Licliens is Cetraria islandica 

 KX ISLANDICUS). Sticta pulmouacea is also used in domestic medicine. 



II. BRYOPHYTA (MOSSES AND LIVERWORTS) ( 9 * 93 - 94 ) 



The Bryophyta or Muscineae comprise two classes, the Hepaticae 

 or Liverworts, and the Musd or Mosses. They are distinguished 

 from the Thallophyta by the characteristic structure of their sexual 

 organs, ANTHERIDIA and ARCHEGONIA, which are similar to those of 

 the Pteridophyta, the most highly developed of the Cryptogams. 

 The Bryophyta and 

 Pteridophyta are accord- 

 ingly regarded as having 

 been derived from a 

 common ancestor, and, 

 in contrast to the Thallo- 

 phyta, they are referred 

 to collectively as Arche- 

 goniatae. 



The ANTHERIDIA or 



male sexual organs are 



stalked, ellipsoidal, 



spherical, or club-shaped, 



with thin walls formed x MSp|/' 



of one layer of cells and 



P n r 1 n si i n v Tin m p r n us FlG ' 375.-Jfarefca polymorpha. A , Nearly ripe antiwridium 



in optical section ; p, paraphyses. B, Spermatozoids tix.-d 

 Small, Cubical Cells, each with 1 per cent perosmic acid. (A x 90, B x 600.) 



of which becomes 



divided diagonally into two spermatozoid mother-cells ( :> ). At maturity 

 the spermatozoid mother -cells separate and are ejected from the 

 antheridium, which ruptures at the apex. By the dissolution of the 

 enveloping walls of the mother-cells the spermatozoids are set free as 

 short, slightly twisted filaments, terminating anteriorly in two long cilia. 

 The ARCHEGONIA are flask-shaped bodies with walls formed of 

 but one layer of cells ; they are sessile or shortly stalked, sometimes 

 also somewhat sunk in the tissue, and consist of a dilated ventral 

 portion and a neck. The ventral portion encloses a large central 

 cell, the contents of which shortly before maturity divide into the 

 egg-cell (Fig. 376 A, o) and the ventral -canal-cell (&")'. The latter 

 is situated at the base of the neck, just below a central row of neck- 

 canal-cells (&'). On the maturity of the archegonium, the ventral- 



