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A TEXTBOOK OF THEORETICAL BOTANY 



Hypoxylon coccineum 



The fruiting body appears as a bright brick-red stroma, about ^ in. in 

 diameter, which may be produced singly or, more often, in clusters together. 

 These clusters are formed upon the bark of dead deciduous trees, particularly 

 beech, and occur during the summer and autumn (Fig. 280). When young 



Fig. 280. — Hypoxylon coccineum. Stromata on Beech 

 bark, about half natural size. 



the stroma is at first covered with fairly long, branched tufts of flattened, 

 olive-brown conidiophores which are covered wdth conidiospores. During 

 the later part of the summer these conidiospores disappear and the colour 

 of the stroma becomes more clearly red. The perithecia are developed 

 as a layer just below the surface covering the whole fruiting body. When 

 mature each opens by a small, somewhat raised ostiole. The ascospores, 

 eight of which are produced in each ascus, are oval in shape and brown 

 in colour. 



A vertical section through the stroma shows it to be differentiated into 

 four zones, which can be seen in a stained section with the naked eye. The 

 innermost zone consists of a loose arrangement of hyphae emerging from the 

 substratum on which the Fungus is growing. Secondly, there is a dome- 

 shaped mass of closely compacted hyphae w'hich lie radially parallel to one 

 another and are made up of empty cells. This zone forms the main mass 

 of the fruiting body and supports the third zone which comprises the peri- 

 thecial layer of loosely woven hyphae in which the perithecia are developed, 

 each being surrounded by a much more closely fitting mass of cells similar 

 to those in zone two. Finally, there is a fourth zone which forms a superficial 

 layer, differentiated into three parts. Firstly, there is a line marking off the 

 fruiting zone by interwoven hyphae which run parallel to the surface of the 

 stroma. This takes a very dark stain. Secondly, there is a space occupied 

 by loose hyphae with dense protoplasmic contents and, thirdly, a surface 

 layer of closely packed hyphae which stain black, and from which at an earlier 

 stage the conidiophores arose. 



In the central region of zone two in the young state, it is possible to make 

 out three distinct types of hyphae which appear to perform separate functions. 

 The most conspicuous are those composed of long, large cells which are 



