22 TEXT-BOOK OF FUNGI 



central homogeneous body in the cytoplasm, apparently 

 formed by the gradual condensation of a mass of granular 

 cytoplasm. The function of this organ appears to be that 

 of bringing the sexual nuclei together. It has since been 

 observed in the oosphere of other species of Cystopus, also 

 in Peronospora. Stevens considers that this organ may 

 be of a dynamic nature, and proposes the name coeno- 

 centrum. After fertilisation this structure disappears. 



In addition to the complex mode of nuclear division 

 described above, nuclei present in vegetative mycelium 

 sometimes divide in a simpler manner, without any forma- 

 tion of a nuclear spindle, etc. Such a method is known as 

 direct division, or fragmentation. By this method several 

 nuclei are often produced in a single cell, as described by 

 Raciborski in certain cells of Basidiobolus. 



Fatty matter or oils are abundant in the cells, and 

 during active growth are in the form of myriads of very 

 minute particles, giving to the protoplasm a turbid or 

 granular appearance. During the resting-stage in spores, 

 sclerotia, hybernating mycelium, etc., these minute 

 particles often collect into large drops, which are either 

 colourless, or sometimes brilliantly coloured. In many 

 of the Discomycetes and others, there are constantly two 

 such oil-guttules at one time called nuclei by systematists 

 in each spore. In some species, but not all, the oil 

 drops assume a brilliant red colour when treated with a 

 solution of alcannin. 



Glycogen was shown by Errera to be abundant in the 

 cells of fungi, more especially in the asci of the Dis- 

 comycetes and the Tuberaceae. It is intimately mixed 

 with the protoplasm, which in consequence appears very 

 refringent. It assumes a reddish-brown or coppery colour 



