4 o 



substratum is large. In the latter case the crust frequently grows thicker than in the former. 

 In this respect it reseml I other species, lor inst. Lithothamnion fruticulosum. It is 



as a rule much burdened with extraneous objects ol one kind or other. Thus the inner or 

 lower parts of a specimen ma) sometimes be almost fully destroyed by boring-muscles, or 



r specimens are traversed with numerous, wider or finer, passages made by worms. In 

 addition, different animals attach themselves to the surface of the plant and become more or 

 overerown by new formed tissue. This contributes to an irregular development of the 

 plant. New crusts are often developed over the primary one, sometimes even more crusts, one 

 above the other, and such new formations often expand over the primary excrescences or short 

 branches. In such cases the branches not seldom become coarser than otherwise (PI. V, 

 So also when germinating plants attach themselves to more or less knotty corals, 

 dead specimens of the same species, or to other calcareous algae with wartdike excrescences 

 or short branches. < >n pi. V, fig. i i is represented a specimen with a coral nucleus. The latter 

 has been covered with Goniolithon Rcinboldi, and this species has in its turn been almost fullv 



red with the species in question. Here and there in the said specimen appear two crusts 

 of . I. erytkraeum, one above the other, the first crust covered with a thin layer of other 

 organisms, apparently lower animals, and then the other one developed over the said layer, 

 both, In 'wever, covering G. Reinboldi. Besides wartdike excrescences or short branches are also 

 in this specimen developed apart from those which have risen from covering up the densely 

 crowded branches of G. Reinboldi. Some uncovered branches of the latter species provided 

 with conceptacles are to be seen in the uppermost part as well as to the right on the quoted 

 picture. The branches of the species in question are on the whole much varying, and in one 

 and the same specimen are often to be found some ones several times thicker than others 

 (PI. V, fig. 2, 4, 5, 10, 12). Sometimes the plant becomes worn and rubbed in the upwards 

 turning part by the action of a strong current, in the same way as often to be seen in 

 Lithothamnioji dimorphum and other species. The edges of such worn branches now and then 

 get covered by new formations of tissue issuing from the next undamaged parts of the plant 

 (PI. V, hg. 7). 



In regard to the structure of the forms above mentioned I refer to my former remarks 

 on this species '). I have there shown that the measures given by Heydrich 1. c. are not 

 correct. The hypothallic layer of the crust is composed of more or less bent rows, the cells 

 of which are up to about 40 u. long, frequently however shorter. The cells of the medullary 

 hypothallium are 10 — 22, frequently 12 — 18 u. long and about 9 — 10 u.. broad. The perithallic 

 cells are partly about 8 u.. square, partly of nearly the same length as those of the medullary 

 hypothallium. However, now and then appear rather irregularly alternating long and short 

 In addition, the minute square and oblique intermediate cells sometimes appear almost 

 everywhere in a section, sometimes apparentlv but here and there. 



Die reproductive organs known are cystecarps and sporangia. The former seem, however, 



I die HEYDRiCH'schen Melobesien-Arbeiten eine sichere Grundlage: — Uet. Kgl. Norske Vidensk. Selsk. 



rondhjem 1901. N". 2. p. (6. 



