MetapJiyta Penicillium. g i 



every conceivable modification of such a primitive type. 

 The threadlike thallus is represented by Ectocarpus, which 

 is otherwise specially interesting as exhibiting an incipient 

 sexual differentiation among its reproductive cells. Lami- 

 naria, again, has a flat and much-branched thallus. Amongst 

 the red seaweeds, or JFloridece, there is great variety of form, 

 and one large group the Corallines derive their name 

 from the fact that they have an incrustation of carbonate of 

 lime which covers the thallus and causes them to mimic in 

 some respects the corals among animals. 



The reproductive cells, the method of fertilisation, and 

 the subsequent changes in the ovum are also somewhat 

 different from the corresponding phenomena in the type 

 selected ; but nevertheless the essential points are precisely 

 similar, and in such a text- book as the present it is not 

 possible to do more than point out the general relationship 

 amongst individual differences. 



SECTION III. FUNGI PENiciLLiUM. 



We have now to direct our attention to a group of plants 

 very different in external appearance and in minute structure 

 from those we have been hitherto discussing, viz. the Fungi. 

 Under this extensive class are included such forms as the 

 common grey moulds, the mushrooms, and many others 

 more or less popularly familiar. In microscopic structure 

 and external configuration they present very great variety, 

 but there are certain well-defined characters which they all 

 possess, and which separate them from the Algae on the one 

 hand, and the higher plants on the other. It will be of 

 advantage to briefly emphasise these characteristics and in 

 some measure to account for them. 



In the first place, it is to be noted that the cells of Fungi 

 contain no chlorophyll, and in the second place that the 

 Fungi live parasitically on dead or living organisms. Can 

 we trace any relationship between these two phenomena? 



