202 PRACTICAL BOTANY 



confirming the conclusions which may be drawn from a com- 

 parison of younger plants, that the whole thallus when young 

 was of a flattened form. 



The following observations are also to be made 



A. Examine the apices of young, actively-growing branches : 

 those branches which bear conceptacles must be carefully 

 avoided, as they do not show such characteristic appearances : 

 the extreme apex is emarginate, or depressed, the base of the 

 depression being somewhat flattened, and marked by a slight 

 groove running in the plane of the thallus. 



B. Compare a number of apices : in some only a single 

 emargination will be seen, in others two, similar to one another, 

 each having the groove at the base, while others again will 

 show an intermediate appearance : from this it may be con- 

 cluded that the single apical point divides into two of equal 

 strength, each of which may develop into a branch of the 

 thallus similar to the original : thus the branching is a 

 dichotomy. 



C. On comparison of a number of branches it may be seen 

 that the development of the two branches of a dichotomy is not 

 equal, one being usually stronger than the other : this leads 

 to a sympodial development of the dichotomous branch- 

 system. 



D. Observe the less regular outline of the ends of those 

 branches which bear conceptacles, the latter being seen in 

 large numbers on those branches : note with a lens the round 

 orifice or ostiole in the centre of each conceptacle. When 

 mature, two kinds of conceptacle may be recognized in this 

 species : they are borne on different plants, and this species 

 may accordingly be recognized as direcious : they are 



a. Conceptacles the contents of which are of a dark olive- 

 green : these contain the oogonia, and are the female con- 

 ceptacles. 



b. Others with yellow or orange contents : these are the male 

 conceptacles, and contain the antheridia. 



E. If those flattened parts of the thallus be examined which 

 do not bear sexual conceptacles, there will be found, scattered 

 here and there, organs of somewhat similar structure, which 



