Porter — Organs of the Common Corlicolous Ramalinae. 27 



or periphery. In no case has the medullary tissue been traced into the 

 peridermal gaps. 



Finally, in the Ramalinae there is a definite " hapteral system " — the 

 term is used tentatively — consisting of one or more main haptera piercing 

 the periderm, with lateral branches in all directions. The whole system 

 resembles the " cortex roots " and suckers of Viseum album, the Mistletoe, but 

 has not their parasitic function to such a marked degree. 



The periderm tissue bordering the main and lateral haptera is crushed 

 into confused, dark-coloured layers, and fragments of cells lie scattered 

 among the hyphae. The lateral haptera taper to a point which is lost among 

 the periderm cells, apparently dwindling into small bundles of hyphae which 

 are capable of changing their direction of growth, and of branching and 

 increasing in diameter. They exert a wedge-like action on the cork layers, 

 as described by Lindau. 



The question therefore arises as to whether the bushy masses in which 

 the Ramalinae often occur are the result of direct development of spores or 

 of soredia, or of "runners" from a parent plant; and further, in the last 

 case, whether the effective runners are superficial or intraperidermal. 



In this connexion it is interesting to note the view of Bornet, 1 that the 

 algae of hypophloeodic lichens are already present when the fungus begins 

 to immigrate, and the opposed view of Frank, 2 that from a germinating 

 spore a protothallus grows into the periderm and only later is colonized by 

 immigrating algae. The sucker-like outgrowths of Evemia prunastri as 

 described by Lindau have been mentioned above. This method of reproduc- 

 tion is undoubtedly very common with the Ramalinae, but probably not so 

 much so as that of the stolon-like forms. 



Assuming that the plant reaches its host from the outside, the 

 bundles of hyphae grow out and penetrate between the periderm cells. The 

 best points of entrance are where a crack in the bark leads to a weak place 

 in the tissue, or a lenticel. Here, too, is a sufficient supply of water or 

 moisture for the growth of the hyphae; consecpiently the hyphal bundle 

 increases in length and diameter, and crushes aside the dead cells of 

 the bark. 



The surface of these hyphal bundles being somewhat of the same character 

 as that of the lichen cortex, the lateral haptera are formed by the intrusion 

 of one or more hyphae between the horizontal layers of periderm, the exact 



1 Bornet, E. Recherches sur les gonidies des Lichens. Ann. des Sc. Nat., 5 scr. Bot. 

 1873, xvii, p. 45. 



- Frank, A. B. Uber die biologischon Verhiiltnissu des Thallus einigeKrustontiechten. 

 Cohn's Beitr. 1877, ii, p. 123. 



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