54 



FIRST GR UP. — THALLOPHYTES. 



another (Fig. 31, ^). Every leaf begins with a node (the basal node) by which it is 

 united with the stem-node, and each leaflet is united in the same way with its primarj'. 

 These basal nodes are the starting-points for the formation of the cortex which covers the 



t/ra£iHs\ longitud: 

 protopiasm, the larger bodies are chlorophyll-corpuscles ; the formation of \ 

 s are contracted by solmion of iodine Magn. 500 times. 



internodes of the stem in the genus Chara, but which is wanting in Nitella. Distinct corti- 

 cal lobes run from the basal node of every leaf, one downwards and one upwards (Fig. 30, r, 

 ;-' , ;-", and Fig. 32) ; as many descending cortical lobes, as there are leaves in a whorl, meet 

 therefore in the centre of each internode with the cortical lobes which ascend from the 



Fig. 31. Leaves of CArt«/)-(7^/jj-; a terminal cell; ("Mast cell but one of a leaf ; .s internodal cells of 

 leaf; iv cell of leaf-node; y" mother-cell of a lateral leaflet and its basal node, from which w and u (the 

 connecting cells) are formed ; br the basal node, which produces four simple cortical lobes and ^ the 

 lateral leaflet. A and C in longitudinal section. B the entire young leaf seen from without with the 

 stipule J- and its descending cortical lobe sr. D middle portion of an older but still young leaf from 

 without. /; transverse section of a leaf-node of the same age as D. 



whorl next below ; but the number of the latter is one less, because the leaf, in the axil 

 of which the lateral shoot arises, produces no ascending lobe. The cortical lobes close 

 up together laterally and form a compact envelope round the internode, in the middle of 



