78 



MORPHOLCGV OF TISSUES, 



bottom of each chamber, after repeated divisions vertical to the surface, sends out 

 protrusions upwards into the cavity ; th,es2 grow in a manner similar to many fila- 



FlG. 65.— Transverse section through tlie horizontal thallus oi Marchautia polyfnorpha ; A central part, furnished 

 on the under side with the leaf-like appendages b, and the rhizoids h (x 30) ; B marginal part of the thallus, more highly 

 magnified; / colourless reticulately thickened parenchyma; o epidermis of the upper side; chl the cells containing 

 chlorophyll ; sp stoma ; s partition-walls between the hypodermal chambers ; u lower epidermis with dark-coloured 

 cell-walls. 



Fig. 66.— Sap-conducting intercellular passages in the young stem of ivy, in transverse section {X 800) ; A,B,C show 

 young passages at^, placed at the boundary of the cambium c and the soft bast ivb ; h the xylem ; ^ in £» and E larger 

 and older passages, lying at the boundary of the bast b and the cortical parenchyma rp. 



mentous Algae, divide, branch, and form chlorophyll, while the whole of the rest of 

 the tissue of these plants is devoid of it. 



