426 



LECTURE XXVI. 



case of a creeping phanerogamous plant, the roots as well as the leaves 

 arise from the advancing apex — the growing-point — which is here projecting, 

 however, so that the youngest leaf and the youngest root are somewhat distant 

 from the apex : hence no proper bud enveloping the growing-point exists at all. 

 What is most important for us, however, is the fact that no cell-formation 

 whatever takes place in the interior of this plant:' no cell- walls exist either in 

 the growing-point or in the completely developed organs. In the cavity of 

 the thick-walled vescicle, however, the ramifications of which constitute the 

 entire plant, numerous bars consisting of cellulose are found, which traverse the 

 lumen of the cell like pillars and rafters, in order to confer greater firmness 

 on the whole structure: in more slender forms of Cceloblastes, however, as 



Fir.. 262.— Cattlerfa craisifolin. The entire plant consists of a vesicle which is not 

 divided into chambers or cells, w the growing-point of the creeping dorsi-ventral shoot- 

 axis .r; deleaves; w roots (nat. size). 



in the common Vaucheria, even these , are wanting. It is now only necessary, 

 therefore, to leave out from what has been said above as to the difference of the 

 three phases of growth all that refers to the cellular structure, which does not exist 

 here, and all the rest applies even to this non-cellular plant. 



A second example may be taken to show the corresponding condition of affairs 

 in one of the more highly organised Fungi. The accompanying figure (Fig. 263) shows 

 the development of a Mushroom, of the genus Agaricus. At / is represented a small 

 piece of the mycelium (w), the thicker filaments of which consist of numerous hyphai 

 running parallel to one another. The mycelium behaves in all essential points like the 

 branched root-system of a higher plant ; at the end of each filament there is a growing- 

 point from which new growing-points are developed as buds. At certain points of this 

 mycelium, at a and b, organs of reproduction are formed, one of which is represented 



