296 PRINCIPLES OF SOIL MICROBIOLOGY 



at the tip by the insertion of regularly spaced septa, and proceeds 

 downward toward the base of the filament; (b) prostate, racemose type 

 in which development of fructifications is more nearly simultaneous. 

 In most species, however, both types are combined. 



The various species are usually characterized by clearly defined 

 septation and have been separated by Drechsler into three different 

 groups, on the basis of the disposition of their septa and development 

 of their spores. 



In the first group, the cross walls in the sporogenous hyphae remain without 

 any very pronounced change and continue to separate the adjacent cells until 

 they have developed into a chain of mature contiguous spores. The insertion 

 of these septa progresses from the tip toward the base and does not break the 

 physiological continuity of the hyphae. Food material is, apparently, readily 

 transported through these septa to the young spores at the termination, since 

 the spores increase in size and may deposit a wall of measurable thickness. 



In the second group the septa apparently split into halves, which are then 

 drawn apart by the longitudinal contraction of the individual protoplasts. 



In the third group the cross-walls first undergo a deep constriction which, 

 by involving the ends of the young cylindrical spores, gives to the latter an elon- 

 gated ellipsoidal shape. The constricted septum now gradually loses its stain- 

 ing properties, and appears to become slightly drawn out in a longitudinal direc- 

 tion. A preparation stained with Delafield's haematoxylin usually shows many 

 old spore chains in which the individual spores are thus connected by hyaline 

 isthmuses. Occasionally an isthmus may be found with a remnant of the old 

 deep staining septum still unchanged in its center. 



Beyond these three types of sporulation another must at least be 

 provisionally recognized, in which septa are either absent from the 

 developing sporogenous hyphae or are not demonstrated by the use of 

 ordinary stains. The protoplast appears to contract at regular inter- 

 vals, yielding a series of non-contiguous spores, held together for a time 

 by the connecting segments of evacuated filament wall. 



The germination of the spores takes place in dilute nutrient solutions. 

 The spore first swells, then one to four germ tubes are produced. The 

 number of germ tubes is more or less characteristic of the species. 



Utilisation of carbon compounds by actinomyces as sources of energy. 

 Various species of actinomyces utilize a number of sugars and higher 

 alcohols as sources of energy, with inorganic sources of nitrogen, es- 

 pecially glucose, starch, maltose and glycerol. Lactose, sucrose and 

 inulin are utilized to a less extent, depending upon the ability of 

 the organism to form the corresponding enzyme. Arabinose, mannite 



