82 PROTECTION OF PLANTS — 1924-25 



History. 



The organism is a iiredinaceous fungus belonging to the so-called lepto- 

 form; it has neither tecia nor uredinia, producing only teliospores. The teliospo- 

 res usually germinate in situ as soon as mature to form promycelia with sporidia. 



Work has been done on this organism by several investigators, including 

 McAlpine, Massee, Plowright, Halsted, Daudeno, Eriksson, Taubenhaus. 

 It is interesting to note that this is one of the organisms upon which Eriksson's 

 mycoplasm theory is based. These workers in general agree that the fungus is 

 carried over the winter. (1) As developing mycelium in the tender young leaves. 

 (2) With the *eed. 



Plowright and Massee also suggested that the teliospores survive the winter 

 on dead or decaying leaves. Daudeno attempted to solve this problem through 

 actual experiments but obtained negative results. Taubenhaus conducted ger- 

 mination tests with teliospores which had overwintered out of doors and obtain- 

 ed germination on several occasions. Taubenhaus does not mention the percen- 

 tage of germination obtained or the percentage of teliospores that lad alread}' 

 germinated in situ; nor did he conduct inoculation experiments with healthy 

 plants to determine if these spores were al)le to cause infection. 



Morphology of Teliospores. 



The teliospores are borne in knobs, composed of different maturit}^; the 

 older spores possessing longer pedicils and extending to the outside of the knob 

 or fascicle. The young teliospores are at first one-celled and are continually 

 being formed even while old spores in the same sorus are in a state of germina- 

 tion. There is considerable variation in the form and size of the teliospores. 

 The normal spore is two-celled, slightly constricted at the center and tapering 

 towards both extremities. The normal spore is 53.8 microns by 15 microns 

 with a range of 38 to 65 microns by 9 to 25 microns. One-celled mesosphores 

 and three-celled spores may be also found. Taubenhaus reports also the 

 occurrence of four -celled spores but they have not come under my attention. 

 Both cells of the teliospore may germinate, sending forth promycelia; but as a 

 rule germination is confined to the apical cell. The general type of promycelium 

 is a long slender tube with the protoplasmic contents of the germinated cell 

 collected at its extremity. After a short time the protoplasmic portion divides 

 into four cells. 



According to Taubenhaus the sporidia are formed in one of two ways. 

 (1) The four cells of the promycelium may separate into free and independent 

 cells. Each of these cells later sends out a little protrusion which elongates and 

 swells up as the contents of the mother cell is gradually passed into it, and thus 

 a mature sporidium is formed, which readily breaks away from the basidial cell 

 and germinates. In the other type the four cells of the promycehum do not 

 break apart but ea h sends out a little sterigma which gradually swells up until 

 the sporidium is formed, into which the contents of the basidial cell is passed. 



