LECTURE XIII. 



PLANTS which, like Mucor, do not possess chlorophyll and are not 

 differentiated into leaves, stems and roots like the higher plants, 

 are called Fungi. Their want of chlorophyll renders it impossible 

 for them to form organic substances from inorganic, and hence 

 they are compelled to derive their food from pre-existing organic 

 substances. The fungi are therefore parasites or saprophytes. 

 Of the plants which we have already studied Yeast and Mucor are 

 fungi. Another very common fungus is Penicillium glaucum 

 commonly called blue mould. Like Mucor it is found growing 

 on various moist organic substances, but it is even more common 

 than Mucor. 



The mycelium of Penicillium resembles that of Mucor in general 

 appearance. It forms a white felt of delicate filaments or hyphae 

 spreading over the surface of the substance on which it is growing. 

 Microscopic examination shows, however, that its hyphse are sub- 

 divided into a number of segments by transverse walls. These 

 segments are cylindrical, and a fairly thick layer of highly re- 

 fringent protoplasm may be seen lying against the inner surface of 

 their cell-walls. The axial vacuole is broken up into a number of 

 spherical droplets by thick diaphragms of protoplasm extending 

 across the cavity of the cylinder. The protoplasm appears homo- 

 geneous and is comparatively free from granules. Some of the 

 few granules which do appear may be shown by staining to be 

 nuclei, others are minute oil drops. The number of nuclei in 

 each segment is small, perhaps 4-8. Hence the segments are 

 small ccenocytes. Another point of difference wherein- the hyphae 

 of Penicillium are unlike those of Mucor is the fact that the hyphse 

 of the former do not taper, but are uniform in thickness right up 

 to the growing tip. The terminal ccenocyte of a hypha has a 

 rounded end and this is filled with protoplasm so that there is no 

 room for a vacuole. Elongation of this ccenocyte takes place just 

 like the elongation of the whole ccenocyte of Mucor, but as soon 

 as it has grown in length so as to equal once and a half or twice 

 the length of the mature ccenocytes of the hyphas a transverse 



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