6 MASS. EXPERIMENT STATION BULLETIN 368 



The conidiophores develop abundantly on all hyphae that lie at the surface 

 of the medium and upon the aerial hyphae when formed. A few develop even 

 below the surface of the medium. They are slender, hyaline and vary in length 

 from a micron or two to 20 or 30 on some aerial hyphae and 10 to 50 microns on 

 a moist surface or in a moist atmosphere. They are usually nonseptate. 



The spores are formed by the abstriction of the tip of the conidiophore. Each 

 is enveloped in mucus, the amount depending upon the moisture of the atmos- 

 phere in which it develops. In a dry atmosphere only sufficient moisture is 

 found to cause the spores to stick together in a head. In a moist atmosphere the 

 globule of mucus swells until it completely envelopes the spores, and careful 

 observation shows the spores floating free in the liquid. This liquid sometimes 

 amounts to three or four times the mass of the spores. The heads vary in size 

 from 10 to 35 microns and contain from two to numerous spores. The spores 

 usually contain granules and are ovoid to cylindric with rounded ends. When 

 the conidiophores are short, the spore masses are found upon the surface of the 

 hyphae. Sometimes, after a conidiophore produces a head of spores, some unde- 

 termined stimulus causes it to resume growth and produce a new head. This 

 phenomenon may occur several times, resulting in masses of spores at intervals 

 along the conidiophores. The spores developed on the moist surface of the medium 

 are usually larger than those of the aerial conidiophores, and frequently continue 

 to enlarge after separation from the hyphae, becoming considerably elongated, 

 even crescent shaped and falcate. When grown to several times their original 

 length they become septate, from one to six or eight septa being formed. These 

 spores then bud at one or more points and develop new conidia of a similar size 

 and shape. In this manner large masses of allantoid, septate conidia are pro- 

 duced, which remain attached to each other by slender threads. Many of these 

 spore masses in the older portion of the culture are distinctly visible to the naked 

 eye. In an atmosphere sufficiently moist some of the erect conidiophores are 

 found to be capped by these long septate spores rather than by the spores of the 

 more usual short, nonseptate type. Every gradation in shape, size, and septation 

 may be observed in a single microscopic mount from some cultures. The spores 

 borne on aerial conidiophores and forming heads of the usual type are from 4 to 

 15 microns in length and one-half to one-third as broad. Those that develop in 

 a moist atmosphere vary from 5 to 15 microns and are one-fourth to one-half 

 as broad as long. Those that develop on the surface of the medium in the presence 

 of an excess of moisture either resemble the preceding or become allantoid or 

 falcate, 20 to 30 by 3 to 5 microns. 



The fungus obtained by the writers, in pure culture from single-spore isolations, 

 is characteristic of the genus Cephalosporium as described by Buchanan. It is 

 extremely variable both in color and in texture. When first isolated from dis- 

 eased wood the colon \- ma\' be rich red, pink, reddish brown, orange, gray, or 

 white. The color is due niainK- to a staining of the agar by the fungus. The 

 colony is cottony and fairly thick while the edge is characterized by feathery 

 irregularities (Fig. 4). The transfer colonies tend to vary widely from the original 

 colonies; some become brilliantly colored and very fluffy (Fig. 4), while many 

 bleach out and the mycelium becomes more recumbent. The stock colonies kept 

 many months in culture by transfers, tend to become white with some streaks 

 of pale green or brown, recumbent mycelium, and a smooth edge; these in turn 

 may produce brown, reddish brown, or reddish colonies with the mycelium tend- 

 ing to return to its original fluffiness. 



The mycelium gives rise to myriads of erect conidiophores each of which bears 

 a head of spores at its tip. To obtain spores for study a tuft of mycelium was 



