SPORES AND THALLIDIA. 



19 



known plants, the genera Morchella and Helvetia {of. fig. 194), Lichens, and also 

 several mould-like forms, notably the Erysiphege, which produce Mildew, and 

 Claviceps, which is the cause of Ergot of Rye. In these plants the ends of the 

 hyphse stand up from restricted areas of the mycelium, some in the form of long 

 clavate tubes, some as delicate filiform paraphyses, the group of tubes and 

 paraphyses being surrounded by other cellular structures in such a manner that 

 the whole has the appearance of a dish or cup or capsule. The protoplasm in the 

 tubes breaks up and forms either ellipsoidal bodies arranged usually in linear 

 series (cf. fig. 194^) or long fascicled threads, which, whilst still inclosed in the 



Fig. 194. — Discomycetes. 



The >rorel {Morchella escnlenta). 2 Longitudinal section from the hymenium of Morchella esculenta showing five fllnmenta 

 e.ich containing eight spores and filiform paraphyses in between them, s Helotium Tuba. * Anthopeziza Winteri. 

 5 reziza vesiculosa. « Helvella In/ula. 7 Helvella fistulosa. 1, *, 5, 6^ 7 natural size ; 3x4; 2x120. 



tubes, put on a stout cell- wall. The name of asci (do-K6s = a leather bag) has been 

 given to these sporangia, and asco.^pores to the spores which they contain. They 

 are destitute of cilia, the distinguishing mark of zoospores, and have no power of 

 independent motion after their extrusion from the tubes, which takes place through 

 a rent at the top. 



There is great variety in the mode of grouping, as also in the envelopment of 

 the sporogenous tubes in different genera and species. When the tubes grow from 

 the bottom of flask-shaped excavations or pits, the whole structure is spoken of as 

 a, perithecium ; if they stand in a shallow patellif orm cavity or on the surface the 



