ALGAE.— CHAKA CEAE. 



SS 



which the ascending and descending lobes fit into one another like the elements of a 

 prosenchyma. The cortex is formed at such an early period, that the internode is 

 covered with it as it elongates, the cortical lobes following its growth accurately as it 



Fig. 32. Development of the cortex of the stem in C//<i'-.iy" ".v'^'-r- ■' 

 stem with the lobes still unicellular ;•. B—D further developme ,t of the 

 the cortical lobes which ascend from the lower leaves, ) ', ?-', r' tho^e 

 leaves ; r, -J the apical cell of each cortical lobe ; ^, a' its internodal c 

 its node; w in Z) the central cell of a cortical node. S denotes evir 

 formations which spring in pairs from the bases of the leaves. 



a very young internode of the 

 ame ; r, ;- indicate everywhere 

 ihich descend from the upper 

 lis ; ;/, m, n the formation of 

 wliere the unicellular stipular 



increases in length and thickness. Each cortical lobe grows like the stem by means of 

 an apical cell formmg transverse segments, from each of which cortical internodal and 

 nodal cells are formed by repeated transverse division ; each of the latter divides by suc- 

 cessive septa into an inner cell next the stem- 

 internode and three outer cells, the middle one of 

 which often grows out into the form of a conical 

 point or knob-like projection, imitating a leaf; the 

 lateral outer cells of the node, on the other hand, 

 follow the elongation of the internode upwards 

 and downwards and grow into longer tubes, so 

 that each cortical lobe consists of three parallel 

 rows of cells, the middle row however having 

 alternately short and long (internodal and nodal) 

 cells. The cortical layer of the leaves which pro- 

 ceeds from the leaflets (secondary rays) is much 

 more simple (Fig. 31, br). There are other leaf- 

 like formations also which arise from the basal 

 nodes of Chara and are called by Braun stipules ; 

 they are always unicellular and either very short 

 or long tubes, and are found on the inner and 

 outer side of the base of the leaf (Fig. 41, s). 



The nodes are the centres of formation for all 

 the lateral members in the Characeae. The root- 

 like structures [rliizoids) spring from the outer cells 

 of the lower nodes of the main shoot ; they are 

 long hyaline tubes, which grow obliquely down- 

 wards and elongate only at the apex. They form 

 an outgrowth of flat cells on the circumference of 



the node, to which they are attached therefore by a broad base; these bases divide again 

 in the stronger rhizoidsand give rise, especially on their upper margin, to small flat cells, 

 from which thin rhizoids are then developed. The tubes of the rhizoids form only a few 



Fig. 33. Rhizoids of Chara fragilis. .1 ex- 

 tremity of a growing tube. B a so-called joint ; the 

 lower part of the upper tube is branching. After 



Pringsheim, niagn. 240 times. The arrows show 

 the direction of tlie 'streaming' of the protopl.ism. 



