52 PHYSIOLOGICAL SERIES. 



B. 26. A similar specimen of E. lactea. The leaves in this plant 

 are minute and borne on the edges of the angular jointed 

 stem. They are soon lost, their duty being performed by 

 the succulent green stem. Royal Gardens, Kew. 



B. 27. A similar specimen of E. globosa having two flower- 

 bearing branches. As in the former specimen the leaves 

 are minute, soon lost, and borne only on the last formed 

 segments of the stem, the jointed character of which is very 

 marked. Royal Gardens, Kew. 



ANIMALS. 



B. 28. Hydroecium o a Hydroid zoophyte (Aglaophenia myrlo- 

 phyllum), with a drawing of the structure of its stem 

 (hydrocaulus). The stem is composed of about seven or 

 eight tubes uniformly arranged in the internodes, but that 

 divide into two bundles at the nodes where they are arranged 

 in one plane. This allows of movement through about 40 

 at the oblique surface of the node. 



Hincks, Brit. Hydroid Zoophytes, vol. i. p. 290. 



B. 29. Portions of a Fan-coral (Melitodes ochracea). From one 

 piece the crust has been removed. Another is in section. 

 The axis is divided into a series of nodes and internodes. 

 At the nodes the spicules forming the axis are loosely 

 arranged, partly fused together at their extremities, or 

 united by a small amount of horny matter. The jointed 

 character of the axis does not increase its flexibility, and 

 apparently only indicates a periodic change in its nature. 



Joints ( = nodes), points of development of organs, separated by 

 internodes that effect the necessary elongation. 



PLANTS. 



B. 30. Nitella flexilis, with drawing of the minute structure of 

 growing end. The stem consists of greatly elongated cells, 

 each forming an internode, their protoplasm is reduced to a 

 thin layer lining the cell-wall, abundant cell-sap occupying 

 the interior ; the nucleus has disappeared by fragmentation. 



