PENICILLIUM. 323 



a clearer enveloping layer, the periplasm. The antheridium 

 is developed shortly after the oogonium in the form of a short 

 club-shaped cell, cut off by a partition wall, and arising either 

 from immediately below the oogonium, on the same hypha, or 

 from some neighbouring hypha. This antheridium grows into 

 close contact with the oogonium. In its contents also a segre- 

 gation into a central fertile portion and a surrounding periplasm 

 is recognisable. No spermatozoids are formed. The anthe- 

 ridium puts out a short cylindrical fertilising- tube, which pene- 

 trates into the oogonium, traverses the periplasm, and reaches 

 the oosphere ; its end opens, and the central contents of the 

 antheridium traverse it, and coalesce with the oosphere, fertilising 

 it. At a later stage the oospore may be found, surrounded by 

 a thick cell-wall, in part at least derived from the periplasm, 

 which has disappeared, so that the oospore lies loosely in the 

 oogonium. The contents of the oospore are densely granular, 

 and with many oil globules. It also is a resting spore, but of a 

 much more resistant character than the resting stage of the gonidia. 

 Penicillium crustaceum, or Blue Mould. Upon the most 

 various objects in damp positions, even if the merest traces of 

 nourishment can be obtained from them, soon is wont to be 

 found the blue-green mould, Penicillium crustaceum, Fries. It 

 is the most widely distributed of all moulds ; we meet with it 

 everywhere, and shall not, therefore, need to seek long for 

 material for examination. It will be, however, most convenient 

 to moisten a piece] of bread, and place it under a bell-jar. Not 

 improbably Mucohneae will first show themselves on the bread ; 

 but soon the, at first, more slowly-developed Penicillium will 

 have supplanted it, and after about a week covers the sub- 

 stratum with a dense blue-green covering. The blue-green colour 

 arises from the gonidia of Penicillium, which, however, only show 

 this colour when in great quantity. We now lift a little material 

 from the substratum, and examine it in water. 1 The mycelium 



1 In the examination of fresh objects in water, it often happens that air 

 clings very tightly amongst the hyphse, and hinders observation. Attempts 

 to remove the air have usually disadvantageous effects upon the preparation 

 itself. In order to render the gonidiophores of these and other moulds free 

 of air, as far as they will admit of it, and yet having their natural distri- 

 bution, the following method may be used : A scrap of the material is laid 

 carefully upon the surface of a drop of glycerine, a drop of alcohol is placed 

 upon it, and the cover-glass is laid on. The extraordinarily violent diffusion 

 currents which are set up usually displace the air quite effectively. 



