BY JOHN SHIRLEY, D.SC. 5o 



■ of the iiclien section is thrown out of focus. In measure- 

 ment they are .02-. 04 x .007-. 018 mm. 



Most curious pores exist in F. pJacorlwdioides, Nyl. 

 They are very narrow and usually at right angles to the 



-surfaces; when they occur beneatli an apothecium they are 

 continued through its hypotheicium and hymenium to 



'.the surface, ' and in the hymenium increase in cross 

 diameter, so that in this jjortion of their course they are 



■conical, while in ths thallus itself they are cylindrical, the 

 whole having the form of a funnel with an extra long 

 tube. In other cases they are conical and larger, reaching 



-.07 X .0035 mm. (Plate II., fig. 2.) Pores of similar 

 infundibuliform shape are also characteristic of P. tine- 

 tor ia, L., in which species they abound in all parts of the 

 thallus. 



In P. olivetorum, Ach. (s. P. tinctorum, Despr.), the 

 jDores are usually perpendicular to the cortices, but are 

 very narrow, .004-. 005 mm., and a.re readily distinguished 

 by their lining hyphee crossing the hyphje of the medulla 

 at right angles. (Plate III., fig. 3.) 



The pores of P. liwhata, Laur., are .026 x .013-.019 

 mm. in size. 



They are usually wider where they oj)en on the upper 

 surface of the thallus, and diminish to a.bout two-tnirds 

 of that diameter at their lower aperture. In some cases 

 they are seen to arise from above the rhizinae which in 

 this lichen are unusually long and stoiit, .26 x .09 mm. 

 These rhizoids are hollow and formed of hundreds of 

 parallel hyphae ; the tips, however are not porous. Froiii 

 the fact that the algal cells are more numerous, and 

 penetrate the thallus more deeply in and along the walls of 

 the pores, and that in P . limbata the canals are connected 

 with hollow rhizinae; and since, when viewed in reflected 

 light, the pores show 'ooi the upper surface not as perfor- 

 ations, but as shallow closed pits, it seems doubtful that 

 the function of these organs is merely to supply the plant 

 with gaseous food, but that they may also take in water 

 for the use of both symbionts, and inorganic food sub- 

 stances for the supply of the chlorophyll-containing algae. 

 (See Plate III., fig. 4.) 



An examination of the thallus of Parmelia laxa, 

 Mull Arg., shows that it possesses oblique capillary tubes, 

 not more than .009 mm. in cross section, and difficult 

 to find, if it were not for the transverse direction of the 

 lining hyphae, and the fact that those threads, forming the 

 inner surface of each perforation, stain more deeply than 



