TILLETIA TRITICI 



225 



pair of primary conidia is left behind as an exhausted and dead 

 structure incapable of further development. The falling away of 

 the H -shaped pairs of primary conidia does not appear to take 

 place if the culture is undisturbed, but it is easily effected by a 



/ 



Fig. 110. — Tilletia tritici. A semi-diagrammatic representation of a pair of con- 

 jugated primary conidia (the authors' primary sterigmata) which was jarred 

 off the promycelium (basidium-body) and fell on to a moist substratum where 

 it produced and shot away a secondary conidium (the authors' primary 

 basidiospore). A, the primary conidia just after falling ; B, a few hours later, 

 they are producing a sterigma (the authors' secondary sterigma) ; C, still later, 

 a secondary conidium (primary basidiospore) is developing at the end of the 

 sterigma ; in B and C the protoplasm is creeping out of the ends of the primary 

 conidia and in C a septum has already been formed ; D, about 1 hour and 

 30 minutes after C, the secondary conidium is fully grown and the protoplasm 

 has almost entirely crept into it, the septa were formed during the protoplasmic 

 migration ; E, lateral view of the pair of primary conidia lying on its moist 

 substratum, showing the sterigma and the secondary conidium projecting into 

 the air, the protoplasm has now completely migrated into the secondary 

 conidium and the secondary conidium is about to be discharged, as is indicated 

 by the drop of liquid which is being excreted at the spore -hilum ; F, about 

 2 seconds later than E, the secondary conidium and the drop have just been 

 violently discharged from the sterigma and are travelling together. Mag- 

 nification, 560. 



slight mechanical shock. Possibly, under natural conditions, the 

 dislodgment of the primary conidia may sometimes be brought 

 about by wind pressure. The mode of development just described 

 and illustrated in Fig. 110 may be regarded as normal or, if not, as 

 only slightly abnormal ; for, in the end, a secondary conidium is 

 produced and discharged into the air and thus a normal climax of 

 development is attained. 



VOL. v. Q 



