76 



BOTANY 



PART I 



lateral axes, arising successively on all sides. These grow less actively 

 than the main axes but can in turn branch similarly. This type 

 of branching is called racemose (cf. the diagram, Fig. 82 b). 



All lateral axes which arise on the axis of the young plant are 



H 



.-U--U". 



H 



a b 



FIG. 82. a, Diagram of dichotomous and, b, of lateral racemose branching. K, Axis of the young 

 plant ; H, main axis ; 1, 2, 3, U, lateral axes of corresponding orders. 



spoken of as branches of the first order ; those which, in turn, arise on 

 branches of the first order as of the second order, and so on (cf. Fig. 

 82). The axis on which a daughter axis arises is termed relatively to 



it a parent axis. Parent 

 axes may thus themselves 

 be daughter axes of the first, 

 second, third, etc., orders. 



Cymose branching, which will 

 be described in connection with 

 the corraus, also occurs in Thal- 

 lophytes. 



In contrast to the TRUE 

 BRANCHING described above, 

 what is known as FALSE 

 BRANCHING is found in 

 some low filamentous Algae 

 and Bacteria. It comes 

 about by the filament break- 

 ing into two portions, still, however, held together by the mucilaginous 

 sheath ; each new end arising by the rupture can grow on as a filament 

 (Fig. 86). When an unbranched thallus is subsequently split into a 

 number of lobes, as in the case of the flat thallus of Laminaria (Fig. 

 351), the term branching is not used. 



The thallus in the Fungi, which do not assimilate carbon dioxide 



FIG. 



,Didyota dichotoma. (f nat. size. 

 After SCHENCK.) 



