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TEXTBOOK OF BOTANY 



finally breaks the epidermis of the leaf. Each cell of the basal layer, 

 like each of the other cells of the fungus up to this time, contains a 

 single nucleus. These basal cells become joined in twos by a dis- 

 solving of part of the walls between each pair of adjoining cells (Fig. 27, 

 D, a); the two cells of each pair have now become a single cell of ir- 



FIG. 27. A, a section through a portion of an infected barberry leaf 

 bearing spring spores on the lower surface and spermatia on the upper sur- 

 face. B, a section through a cluster cup, showing the spring spores. C, a 

 section through a cavity in which spermatia are being formed. D, the 

 formation of spring spores : a, the union of two gametes in the basal layer 

 of the cluster cup; b, the two nuclei of the zygote have divided; c, the 

 zygote has cut off a two-nucleate cell ; d, the zygote has formed a chain of 

 spring spores (e) alternating with small cells (/) which will soon disappear. 

 D after Christman. 



regular shape, containing two nuclei. The two nuclei of each such 

 irregular cell now divide, one of each pair of daughter nuclei passes 

 to the upper end of the cell, and this end is cut off as a small two- 

 nucleate cell (Fig. 27, D, b and c). Then the two nuclei left in the 

 large lower cell divide again, and another small two-nucleate cell is 

 produced just below the first one. 



The process of division is repeated again and again, so that a long 

 chain of two-nucleate spring spores is formed (Fig. 27, D, d). 1 From 



1 Really each cell of the chain in turn divides into two cells, of which one (the 

 upper) becomes a spore ; the lower one remains small and very soon breaks down 



