DESCRIPTIVE CATALOGUE 



OP 



CRETACEOUS PLANTS. 



Group THALLOPHYTA. 



Plants with great variety of external morphology, but with- 

 out differentiation into true root, stem and leaf. The plant 

 body may consist of a single cell, a small number of cells, or may 

 be a large, complex organism many feet in length. The higher 

 members of the group show both internal and external structures 

 suggestive of some of the features of the Vascular plants, but 

 they are distinguished from them by the absence of true roots 

 and the lack of differentiated vascular elements. Keproduction 

 may be by simple, unisexual spores, but in the majority of forms 

 there is some trace of sexuality, and in some the reproductive 

 processes are exceedingly complex. 



As no member of the group produces woody or scleren- 

 chjmatous elements, the parts are all soft and are very liable 

 to decaj'. This perhaps accounts for their scarcity among the 

 fossils, though many purely physical appearances have been 

 mistaken for them. Few reliable determinations of members 

 of this group have been made, except among the Calcareous 

 Algse, which secrete for themselves a coating of carbonate of 

 lime. 



Class ALG-aS. 



Plants with vegetative body varying from a single cell to a 

 complex, multicellular structure. All forms are provided with 

 chlorophyll, which is masked by other pigments in some of the 

 groups. 



