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SMITHSONIAN MISCELLANEOUS COLLECTIONS [VOL. 47 



BORING ALGJE 



One incidental result of the decalcification of so many freshly pre- 

 served corals has been the revelation that the madreporarian skeleton 

 is almost universally infested with minute, filamentous, boring algse. 

 Every fragment decalcified, with the exception of pieces from near 

 the growing apex of branching colonies, has yielded material of a 

 fluffv texture within the spaces previously occupied by the corallum. 

 Particles representing the organic matrix of the skeleton are mingled 

 in the fluffy mass, but by far the greater part consists of microscopic 

 algal filaments, which are usually green in color but occasionally red. 

 Further, on cleaning away by maceration the animal tissues of freshly 

 collected corals, the skeleton is frequently found to be green or pink 

 in color, either as a whole or in part ; and closer examination proves 

 this to be due to the presence upon the surface and within the 

 calcareous substance itself of closely ramifying filaments of green 

 or red alga. Not only the West Indian corals have been found thus 

 infested with boring plants, but fragments from many Pacific species 

 and even fossil corals of Paleozoic times have disclosed the same. 



Of the green algae two forms only have been found : one in which 

 the filaments are provided with transverse walls, and another with 

 continuous tubes, belonging to the group of the Siphoneae. Both 

 are extremely variable as regards the size, form, and extent of 

 branching of the filaments, and are often closely intermingled in the 

 same fragment of coral. Only one species of red alga has been 

 found, and this is represented by simple, closely intermingled fila- 

 ments. The non-septate green species frequently bears club-shaped 

 or spheroidal enlargements which contain spores, but no reproductive 

 bodies have been found on the others. No fungi have been observed, 

 so that probably the saproleginous Achlya penetrans of other writers 

 is reallv an alga; old preserved material does not show the chloro- 

 phyll granules, although so obvious in fresh coralla. 



Much significance has been attached in recent years to the presence 

 of boring algse and fungi in calcareous organisms other than corals, 

 especially in shells of mollusks, both living and dead. Moreover, 

 the corroding activity of these Thallophytes has been shown to play 

 a very important role in the ultimate disintegration of dead calcareous 

 matter, reducing the carbonate of lime once more to the soluble 

 state. In this respect they are to be compared with the putrefactive 

 bacteria in their action on dead organic matter generally. The 

 physical and chemical processes involved in the entry of delicate 

 plant filaments within the dense calcareous structures are not fully 



