78 MORPHOLCGY OF TISSUES. 
bottom of each chamber, after repeated divisions vertical to the surface, sends out 
protrusions upwards into the cavity ; these grow in a manner similar to many fila- 
FlG. 65.— Transverse section through the horizontal thallus of Marchantia f>oly7>iorpha ; 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; j 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 lub ; h tl:e xylem ; in Z> 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. 
