MOSSES. 43 



resemblance to some forms of the fresh-water Alg«. 

 Subsequently little buds arise on various parts of the 

 protonema, which send down rootlets into the matrix, 

 and become rudimentary moss plants. Thereafter 

 progress is normal, by the production of stem and 

 leaves, and they partake of a perfect resemblance to 

 the original moss from which the spore was derived. 



This intercalation of a more or less thalloid inter- 

 mediary between the spore and young plant has 

 somewhat of an analogue throughout most of the 

 cryptogamia. Its greatest perfection is in the ferns, 

 where the prothallus develops sexual organs, as a 

 true alternation of generations ; sinking in the mosses 

 to a protonema, on which young plants arise by 

 budding. In the lichens these are represented by 

 the thallus, which bears the apothecia, and some- 

 times remains long as a barren thallus, including the 

 whole vegetative system of the plant. But in fungi 

 it becomes degraded into mere threads of mycelium, 

 or consolidated into hybernating sclerotia. Lastly, 

 in the Algae it may be normally obsolete, or, repre- 

 sented by active zoospores, eventuate in a combina- 

 tion of vegetative with reproductive systems. Thus, 

 then, in all we may recognize a middle state between 

 the mature ovum and the young plant, which may 

 be either a prothallus, a protonema, a thallus, a 

 mycelium, filamentous or compact, or a zoospore. 

 Some may regard this as a fanciful analogy, but, if 

 so, it will not jeopardize the facts, which will remain 

 stable amid the ruins of the hypothesis. 



