62 DISEASES OF FIELD & GARDEN CROPS. [OH. 



at A is shown in section. This upper part of the fungus 

 is technically termed the stroma, meaning a coverlet ; and 

 immediately under the surface of this clublike stroma or 

 coverlet are numerous minute embedded flasks, as illus- 

 trated. These flasks are termed perithecia, in reference to 

 their function, which is to enclose a number of transparent 

 bladders or thecce. The number of contained bladders in 

 each perithecium is about one hundred. At C some of 

 the perithecia embedded in the stroma are enlarged five 

 diameters, and the upper perithecium is shown in the act 

 of discharging the contained spores. If, with the point of a 

 needle, we remove a few of the transparent thecae, bladders, 

 or asci, and magnify them 200 diameters, we shall see them 

 as at D E F. An ascus is represented, packed with its 

 eight spores, in situ at D ; the top of the open ascus is 

 shown at E with the eight hairlike spores escaping, and 

 F shows an empty ascus after all the spores have been 

 expelled. If we now leave the Torrubia and examine the 

 truffle, we shall find its inner mass densely packed with 

 its own spores, also contained in transparent bladders ; 

 but the truffle spores are spherical in form, blackish-brown 

 in colour, and packed in twos, threes, or fours in the asci 

 (not in eights as in the Torrubia}. Some of the Elapho- 

 myces spores in an ascus are illustrated at G, enlarged, 

 like the asci and spores of the Torrubia, to 200 diameters. 



The spores, or necklace-like chains of sporidia, of Tor- 

 rubia ophioglossoides, Tul., are amongst the most wonderful 

 objects of the vegetable kingdom. One of the eight chains 

 from an ascus is enlarged to 1000 diameters at H. 



To sum up the characters, the Isaria is perfected early 

 in the season, and is capable of reproducing itself by its 

 own spores or conidia, as shown in Figs. 19 and 20. 

 Later in the season the mycelium of Isaria often produces 

 a Torrubia, A, Fig. 22 ; and the latter plant, instead of 

 producing free, dustlike spores from the naked apex of 

 its branches, as in the Isaria, produces spores or sporidia 

 in the form of long chains enclosed in transparent flasks, 



