40 



PLANT LIFE. 



composed are called hypha;. Each is the result of growth 

 from a single cell, and is comparable to the thread-like body 

 of the filamentous algs. 



There is, naturally, a great variety in the hyphfe of differ- 

 ent species of fungi. Some are relatively large ; others very 

 small ; some of even diameter and caliber, others irregular 

 and with unequally thickened walls ; some very thin-walled, 

 others very thick-walled. Between these extremes is to be 

 found a complete gradation. 



They grow in length at the apex only. In man}' kinds 

 partitions are formed at more or less regular intervals, as the 

 growth in length proceeds. In others no partition-walls are 

 formed, though division of the nucleus takes place. E\'en 

 when transverse partitions are formed, they do not separate 

 the filaments into cells, but each chamber, or sometimes the 

 whole filament, is a cccnocyte. 



49. Branching. — As the hyphre elongate, branching may 

 occur. If a Ijranch is to be formed, a limited area of the cell- 

 wall begins to grow more rapidly than the rest. This allows 

 a slight bulging of the growing region; 

 the swelling increases and soon takes 

 the form of a branch, like the main 

 axis. It may remain short or continue 

 to grow indefinitely in length. Com- 

 monly a septum is formed at the base 

 of the branch. If such a branch arises 

 first as a minute pim])le, so that it 

 remains connected with the parent axis 



Fig. 48. — Beer-yeast{.S"/i(-iV;/;.;vi- ^ 



myces ceretnsit^). <!, a full- by a Small ncck, and has only limited 



jirown plant with a branch ^ 



(bud) partially developed, ^.growth in length, it is Called a bud 



tr, colonies formed by budding, ^ 



the individuals still attached, and the proccss is known as buJJinQ- 



Magnified 750 diani, — After --^ 



i^'="5- (fig. 48). Such branches are usually 



easily broken off, thus readily producing independent plants. 

 (See further under Reproduction, ■[ 302.) In some species of 



