MORPHOLOGY 



13 



Fig. 8. — Dictyota dicliotoma. (f na t- size.) 



growth in the brown sea-weed Cladostephus verticillatus (Fig. 7). 

 The great variety in the form of the larger Fungi and Lichens, 

 by which they are distinguished as club-, umbrella-, salver-, or 

 bowl-shaped, or as bearded ^ 



or shrub-like, is due to the \J( [(a- 



union or intertwining of 

 apically growing filaments. 

 This manner of develop- 

 ment is limited to Fungi 

 and Lichens. In other 

 cases, the more complete 

 segmentation exhibited by 

 the lower plants results 

 from the differentiation of 

 independently branching 

 filaments and bands. 



As the apex itself may 

 undergo successive modifications through continuous bifurcation, as 

 in the case of Dictyota dicliotoma (Fig. 8), it does not always 



necessarily follow that the for- 

 mation of new members must 

 proceed directly from the ori- 

 ginal apex. The highest de- 

 gree of external differentiation 

 among the lower plants is met 

 with in the group of the red 

 sea-weeds (Rlwdophyceae). Many 

 representatives of this class re- 

 semble the higher plants in the 

 formation and arrangement of 

 their members ; Hydrolapathum 

 sanguineum (Fig. 9), for ex- 

 ample, as is indicated by its 

 name, has a strong resemblance 

 to a species of Rumex, and affords 

 a remarkable illustration of the 

 analogy of form existing be- 

 tween plants phylogenetically 

 unconnected. On account of a 

 supposed phylogenetic connec- 

 tion between the lower plants, 

 they have been collectively de- 

 signated Thallophytes, while 

 the body of the individual 

 organisms, having neither true leaves nor stem, is referred to as a 

 thallus. In contrast to the thallus, the body of the higher plants, 



Fig. 9. — Hydrolapathum sanguineum. (£ nat. size.) 



