20 



GENERAL MORPHOLOGY. 



concerned the process may go on according to two different types, 

 wliich are diagrammatically represented in Figs. 103 and 104. 

 Let us first consider type I. with reference to Fig. 103. The 

 upper extremity of the conidiophore, a, which has sprung from 

 the mycelium, puts forth (b) on its crown an enlai-gement, 

 Avhich then (c) becomes bounded by a septum, thus forming the 

 first exospore. The conidiophore {rl) then stretches a distance 

 equal to the length of a spore, and (e) undergoes constriction so 

 as to form a second spore. This operation may be repeated a 

 second time (/, g), and even more often, thus forming a chain of 

 spores (h), the topmost of which (i) is the oldest, and the lower- 

 most (4) the youngest. The serial order of their production is 

 arranged from the tip towards the base of the conidiophore, or 

 the point where it branches from the mycelium ; and conse- 

 quently the conidia are said to be basipetal. The ultimate 



Fig. 103.— Diagrammatic sketch of the formation of conidia, according to type I. 

 For explanation see text. (After Zoj)/.) 



length of the conidiophore is the same as at the outset no 

 matter how many spores have been formed thereon. The sur- 

 mounting chain of conidia breaks away veiy easily ; even a slight 

 draught of air being able to bring this about, and thus distribute 

 the spores in the form of a fine dust. Owing to then- similarity 

 to this latter the exospores have received a second appellation, 

 and one by which they are more generally known, viz. conidia 

 (from the Greek Koi'ia = dust). An example of this type is 

 afforded by the well-known bread mould, Penicillium (jlancum. 



In contrast to the foregoing process, wherein the conidio- 

 phore alternately increases in length and constricts to form 

 a spore, is the second type, illustrated in Fig. 104. Here the 

 conidiophoi'e (a) ceases to grow in length as soon as the first 

 spore {I)) has been formed by constriction at the apex. This spore, 

 when fully developed (c), puts forth a protrusion (cZ), which then 

 grows to a second spore {e). This in turn continues the task of 

 its predecessors, and consequently forms a third spore (/), which 

 develops a fourth (7), and so on. Hence, in this type, the serial 

 order of production of the spores {Ji.) is the reverse of that in 

 the first type, i.e. proceeds from the base towards the apex, and 



