Metaphyta Penicillium. 99 



and requiring a long time for its proper development. The 

 chances of the ultimate formation of embryos in this manner 

 are obviously much fewer than if the plant were not a para- 

 site, and if its embryos were rapidly formed as in Fucus. 

 There might be a possibility under these circumstances of 

 the plant being entirely destroyed off the face of the earth 

 were it not that the very efficient asexual mode of multipli- 

 cation comes, so to speak, to the rescue, so that, by means 

 of the simple vegetative budding above described, a plentiful 

 supply of new plants may be formed with a large margin for 

 waste. The spore stage is not represented in FUCUS, where 

 the, in that case, very efficient sexual method is amply 

 sufficient to replenish loss of individuals and spread the 

 seaweed wherever the salt-water flows. 



By way of summary, then, we may say that while the 

 thallus of Fucus produces male and female cells, the latter 

 of which, after fertilisation by the former, develop into 

 thalli similar to that from which we started, the thallus of 

 Penicillium produces male and female cells, similarly capa- 

 ble after fusion of reproducing a thallus, but is able also to 

 separate off certain asexual cells, conveniently termed 

 spores, which may develop into thalii capable of forming 

 either another and yet another generation of spores, or true 

 sexual organs and a series of embryos. 



If we agree to term the thallus of Fucus the sexual gener- 

 ation, as being the generation which produces sexual cells, 

 then we would write its life-history thus : 



ST--<? + $ ST <?+ ? 



and so on, where S T stands for the sexual thallus and $ 

 and $ for the male and female sexual cells respectively. 

 If we agree, in like manner, to call the spore-bearing thallus 

 an asexual generation, and to denominate it by the letters 

 AST and the spore by the symbol o, we might write the 

 history of Penicillium thus : 



H 2 



