182 Plant Biology 



tips of the hyphae which line them. The pycniospores may be carried 

 by insects and are of two types, known as plus and minus. A plus spore 

 fuses with a minus spore to form a mycelium which produces chains of 

 yellowish-red, spring spores called aeciospores (e'siospor) (Gr. aecium, 

 injury) in small cuplike aecia on the lower surface of the barberry leaves. 

 The aeciospores are windblown to young wheat plants in the spring, 

 where their hyphae again form uredospores to complete the life cycle 

 (Fig. 67). 



ureclospores^ 



'•••'•r*.:^ "^ 



"^''\f<:/ pycniospores 



pycn/um 





telfum 



basid/o 



spore \ 



germinafing 

 basidiospore - ., 



--infercoflary ce// 

 sepcfraf/hof 

 aeciospores 



basidium 



germ/nat/n^\^ 

 feliospores 



Fig. 67. — Wheat rust (Puccinia graminis). A, Section of leaf through a 

 pycnium; B, section through an aecium in a barberry leaf; C, section through a 

 uredinial sorus, showing unicellular, rough uredospores on slender stalks; D, sec- 

 tion through a telial sorus, showing two-celled teliospores on long pedicels; E, 

 germinating teliospores — left, both cells of the spore germinating; right, only the 

 apical cell germinating; the germ tube has been transformed into a basidium, 

 from each cell of which a basidiospore has been or is being formed. A germinat- 

 ing basidiospore is also shown. (By permission from Botany, by Hill, Overholts, 

 and Popp. Copyright, 1950. McGraw-Hill Book Company, Inc.) 



