62 



.PLANT STKUCTUKES 



Here must probably be included the yeast-fungi (Fig. 

 48), so commonly used to excite alcoholic fermentation. 



/ • ■ , - 



Fig. 47. The common edible morel {Morchella 

 esculenta). The structure shown and used 

 represents the ascocarp, the depressions of 

 whose surface are lined with asci contain- 

 ing ascospores. — After Gibson. 



Fig. 48. Yeast cells, reprodu- 

 cing by budding, and form- 

 ing chains.— Caldwell. 



The " yeast cells " seem to be conidia having a peculiar bud- 

 ding method of multiplication, and the remarkable power 

 of exciting alcoholic fermentation in sugary solutions. 



3. iEciDiOMYCETES (yEcidium-Fungi) 



45. General characters. — This is a large group of very 

 destructive parasites known as " rusts " and " smuts." The 

 rusts attack particularly the leaves of higher plants, pro- 

 ducing rusty spots, the wheat rust probably being the best 

 known. The smuts especially attack the grasses, and are 

 very injurious to cereals, producing in the heads of oats, 

 barley, wheat, corn, etc., the disease called smut. 



