DEVELOPMENT OF PLANTS 



241 



In the common blue mould, Penicittium, these erect hyphae are 

 broom like (Fig. 152, B) and the spores are formed from the 

 tips of the branches vary much after the manner of the budding 

 of the yeast cells. The tip of a branch buds out into a spherical 

 cell that is finally cut off from the stalk, thus forming the spore 

 (Fig. 152, C). This process is repeated again and again just 



FIG. 151. Other common forms of the Spheriales: A, habit of Hysterio- 

 graphium, on a dead twig. B, ascocarps enlarged. C, ascus enlarged, show- 

 ing character of ascospores. D, Daldinia. E, section of the same, showing 

 that the stroma forms a concentric stratum of ascocarps, as, each year. F, 

 Xylaria. G, the same with branch cut off to show the layer of ascocarps 

 on the periphery of the stroma. 



below each successive spore and in this way chains of spores 

 are formed. It will be noticed that many single spores are found 

 instead of a large sporangium which contains many spores as 

 in the case of Mucor. These spores are sometimes regarded 

 as sporangia which have become reduced in size and contain but 

 a single spore. In Aspergillus, a fungus common upon preserves 

 and upon herbarium plants that have not been sufficiently dried, 

 the spores are developed from very short branches that arise 

 from a bulbous swelling at the apex of the erect hyphae (Fig. 

 152, A). The color of the spores, as in Mucor, is the cause of 



the characteristic blue or brown color of the fungi. These ex- 

 16 



