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©272, “Structural and Physiological Botany. 
- 
ductive cell, the zygospore. This continues to grow, andat. 0) & 
length attains a diameter of more than o72mm. To this 
class belong also the sfermatza of the Ascomycetes (Fig. 
405), Uredineze, and some other Fungi, which are believed, 
THN WAIN SW ww foe 
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bem pad 
Fic. 405.—An ascus of Péeztza sur- Fic. 406.—Pucciuta graminis: ab 
rounded by filaments from which cells of the leaf of the host -(Berdberis 
spermatia are being detached vulgaris); the. spermatia c are 
(greatly magnified). escaping from the spermogonium 
(after De Bary, x 200). 
and probably not without reason, to contain sexual elements. 
They are small, usually narrow, rod-like bodies which are 
abstricted singly or in rows (as in the Uredinez) from the 
apex of narrow filaments (sterigmata or basidia). ‘They are 
almost always formed in large numbers, and often in special a 
receptacles, the spermogonia (Fig. 406). 
It has long been known that certain forms of Fungi are 
always produced in a definite order of succession with re- 
spect to one another ; but Tulasne was the first to show, in 
1851, that one and the same species may have organs of 
reproduction of several different kinds, and that the phe- 
nomenon referred to has the most intimate connection with 
their course of development. Still more recent investigations 
have shown that many Fungi, in addition to this Polymorphy - 
of the reproductive organs, exhibit also, in the course of: — 
their development, a regular A/ternation of Generations ; so ve 
that many genera which had previously been considered dis: 
