4 GENERAL MORPHOLOGY. 



In mycelial structui-e and several other particulars, the members 

 of the first subdivision bear a remarkable resemblance to certain 

 unicellular algae, for which reason they have received the name 

 Phycomycetes, or algic fumji. On the other hand, the Eumycetes 

 of the second group, with septated mycelia, bear the group- 

 name Mycomycetes. In comparison to the others these latter 

 stand on a higher plane of development, and are almost exclu- 

 sively aerial ; whereas the majority of the Phycomycetes still 

 incline to subaqueous existence. The following scheme will 

 easily fix the foregoing classification in the reader's memory : — 



rCormophyta 



Vegetablel {^'iZ^^rl^'^^l':^ 



KiDgdom j 



KThallophyta' 



Fungi (Mycetes 

 (not producing 

 chlorophyll) 



[Eumi 



ge" 

 I bn 



chlorophyll) (Eumycetes (Acro- 

 genous true 



branchings) 

 Schizomycetes 

 ^Fission fungi) 



'Mycomycetes 

 (septated 

 mycelium) 



Phycomycetes 

 (unicellular 

 mycelium) 



S 



s 218.— The Typical Mycelium. 



We will now consider the development of the mycelium 

 of a Mycomyces from its spore, Fig. 93 helping to make this 

 clear. Soon after the tubular buds have sprouted from the 

 spore, a septum forms between the spore and each of the 

 buds. The tube then increases in length, and develops in 

 its interior a septum which divides it into two cells, the 

 one nearer the spore (or centre of growth) being termed the 

 inner cell, whilst the outer one is called the terminal or 

 crown cell. Now, whereas the inner cell ceases to increase in 

 length the crown cell continues to grow longitudinally, and in 

 turn develops a septum, whereby an inner cell (of the second 

 order) is again formed ; and this operation is repeated at con- 

 venience. Meanwhile the inner cells are not inactive, since, 

 although they do not increase in length, they throw out lateral 

 projections, which develop into branches separated fi-om the 

 inner cell by septa. These branches grow longitudinally, and 

 separate into a crown cell and a secondary inner cell by develop- 

 ing another septum, an operation repeated by the crown cells as 

 often as external circumstances will admit. This faculty of the 

 inner cells of the first order is also shared by those subseqiiently 

 formed, so that we have lateral branches of the third, fourth,, 

 and other orders. The whole of these hyphse or mycelial threads 

 together constitute the mycelium. The serial order in which 

 the inner cells begin to throw off lateral branches is, as a rule, 

 in accordance with their age, the oldest starting first. Conse- 

 quently, the development of the mycelium proceeds laterally 

 from the spore (the "basis") towards the periphery or apex of 

 the mycelial thread, such a mode of growth being termed basi- 



