THALLOPHYTES 
77 
Ergot fungus (Claviceps purpurea). This is a common parasite on 
young ovaries of grasses, especially rye. The ascospores infect the 
ovaries in early summer, and on account of the growth of the mycelium 
the ovary becomes enlarged and deformed. The mycelium produces 
abundant sporophores, the conidia being abstricted in clusters, and also 
excretes copious honey dew, which is sought by insects, and in this way 
the embedded conidia are carried to other ovaries. 
After the absorption of the tissues of the ovary, the mycelium becomes 
transformed into a compact, parenchyma-like mass, the sclerotium 
(fig. 1120). These elongated, dark violet, often curved sclerotia, re- 
placing the ovaries and projecting from the spike, are the so-called 
ergot, the source of the astringent drug that bears the same name. The 
sclerotia fall to the ground and pass the winter. In the spring, when 
the rye is in flower, the sclerotia produce radiate 'patches of hyphae, 
that in turn give rise to 
long-stalked, rose-colored, 
globular heads (stromata), 
in which are numerous 
sunken perithecia which 
communicate with the 
surface through porelike 
openings. The ascospores 
are remarkable in being 
very long and filiform, and 
are carried by the wind to 
the flowering spikes. 
Xylaria, which belongs 
FIGS. 183, 184. Xylaria: 183, club-shaped stro- 
here, IS a very common ma t a arising from the sclerotium, the surface perfo- 
saprophyte, forming con- rated by the porelike openings of the perithecia; 
spicuous hard black masses l84 ' section th u roagh a Penthecium showing asci and 
paraphyses ; the ascus wall is so delicate that the row 
on dead wood. From the of asco s P ores is the conspicuous feature. 
sclerotium there arise club- 
shaped stromata (fig. 183), whose surfaces are perforated by the very 
numerous porelike openings of the perithecia (fig. 184). 
(h) Laboulbeniales 
This is a remarkable group of fungi parasitic on insects, especially aquatic forms. 
The sexual apparatus is much like that of the red algae, the procarp consisting of 
carpogonium, trichogyne, and auxiliary cells ; and the antheridia producing sper- 
