862 INTRODUCTION TO CRYPTOGAMIC BOTANY. 



a Porothelium, on the other hand, be compared with some of 

 the white Tapezice or Solenia, the external resemblance is 

 almost perfect ; but the one have asci, the other sporojjhores. 

 If these scattered pores become approximate, we have the 

 higher forms of Porotheliumi and Fistulina, which appears 

 to us a true Polyporoid ; and if they are connate through their 

 whole length, we have, according to the degrees of confluence, 

 a Boletus, Polyporus, or TraTnetes-, We have here, again, the 

 same series of forms as amongst the Hydnei, with the same 

 variety of substance, colour, and sculpture ; and, as in the 

 former case, the size, length, division, &c., of the hymenial 

 processes afford an infinite variety of characters. Where the 

 tubes are only slightly connected so as to be divisible, we have 

 Boletus or Favolus; where they are thin but not divisible, a 

 Polyporu^ ; and where the trama is thick and passes sensibly 

 into the substance of the pileus, a Trametes. Large alveolar, 

 rigid, hexagonal pores are the characteristic of Hexagonia. In 

 Fistulina the pores are from the first perfectly distinct, and 

 their tips are always free and studded with little granules, which 

 give them a flowery aspect. In a few genera the pores are far 

 less typical, formed rather by elevations of the hymenium anas- 

 tomosing so as to form little arese, than regular pores. Meru- 

 lius, therefore, is on the one side confluent with the superior 

 order ; and on the other with Craterellus. Laschia is remark- 

 able for its gelatinous substance, and approaches very near to 

 Exidia. 



396. The number of good species contained in the genus 

 PolypoTUS is immense, and increasing every day. They may 

 be divided into three great masses — the tropical, sub-tropical, 

 and European species. Many of the tropical species, as P. 

 sanguineus, P. xanthopus, &c., are found wherever the tem- 

 perature is sufiiciently high ; while, on the contrary, many are 

 local. The same species may occur in India and Cuba, with- 

 out any intermediate station. Some species are common to 

 the Arctic and Antarctic hemispheres, while others are con- 

 fined to each. A few species, as P. lucidus, igniarius, versi- 

 color, &c., are found in every variety of climate. In general, 

 the species which affect warmer climates are not distinguished 



