64 PHARMACEUTICAL BOTANY 



Lichenes arej like the Fungi, divided into several sub-groups. A perfect 

 lichen usually consists of a thallus, or vegetable apparatus;, apothecia, 

 or organs of fructification, and spermogonia, or organs of fertilization. 



DIVISION n.— BRYOPHYTA 



Plants showing a beginning of definite alternation of generations, 

 i.e., gametophyte (sexual phase) alternating with sporophyte (asexual 

 phase of development) in their life history, the two phases being com- 

 bined in one plant. 



SUBDIVISION I.— HEPATIC^ OR LIVERWORTS 



Plants of aquatic or terrestrial habit whose bodies consist of a rather 

 flat, furchate branching thallus or leafy branch which is dorsiventral 

 (having distinct upper and lower surface) ; the upper surface consists of 

 several layers of cells containing chlorophyll, which gives the green 

 color to the plants; the lower surface gives origin to hair-like out- 

 growths of the epidermal cells serving as absorptive parts and called 

 rhizoids. Upon the dorsal surface of this thalloid body (the gameto- 

 phyte) cup-like structures are produced called cupules which contain 

 special reproductive bodies called gemmae, these being able to develop 

 into new gametophytes. The sex organs are of two kinds, male and 

 female. The male organs are termed antheridia, the female, arche- 

 gonia. The antheridia are more or less club-shaped, somewhat stalked 

 organs consisting of an outer layer of sterile cells investing a mass of 

 sperm mother cells from which are formed the spirally curved biciliate 

 antherozoids, or male sexual cells. The archegonia are flask-shaped 

 organs consisting of an investing layer of sterile cells surrounding an 

 axial row of cells, the neck canal cells, ventral canal cells and the 

 egg or female sexual cell. Every cell of the axial row breaks down 

 in the process of maturation with the exception of the egg which remains 

 in the basal portion. Both antheridia and archegonia generally arise 

 on special stalks above the dorsal surface. After the egg is fertilized 

 by an antherozoid, the young embryo resulting grows into a sporo- 

 gonium (the sporophyte) consisting of a stalk portion partly imbedded 

 in the archegonium surmounting a sporangium or capsule in which 

 spores are produced. When mature the capsule splits open discharging 

 the spores. The spores on germination develop into a protonema or 

 filamentous outgrowth which later develops the thallus. 



