37 



ssgsg 



apparently Bryozoa, even filling the intervals between some crowded and in part dead branche 

 These Bryozoa are again for a great part covered with a crust of the plant. The incrustment 

 rises from the nearest branches alive, and by and by it develops new branches too. Still in 

 other specimens new crust-like formations are developed over dead branches or extraneous objects, 

 sometimes issuing from branches being alive, sometimes, as it seems, formed from germinating 

 plants which have attached themselves to the said branches. In this case too new branches are 

 developed in a rather early stage of the said formation (PI. I\ T , fig. 5 and 10 — 11). In the 

 specimen last quoted a small and young specimen of the same species has been brought into 

 contact with two of the outermost branches. Then a crustlike formation some mm. broad has 

 been developed, issuing from both the said branches in a semicircle around one of the branches 

 of the said young specimen, thus fastening the latter, although but partially anastomosed with it. 

 These cases seem to indicate that the species perhaps sometimes attaches itself to small objects, 

 at first forming a crust over the latter, and afterwards loosening itself. In addition broken or 

 loosened branches probably continue their growth freely at the bottom. 



A section parallel to the longitudinal axis of a branch exhibits superposed, generally 

 clistinctly separate and rather regular cup-shaped layers of tissue, the cells of which are arranged 

 in rows radiating in the shape of a fan, such as in most of the branching species of this genus. 

 The cells of the medullary hypothallium are rectangular, often however with somewhat rounded 

 corners, the length being frequently twice the 

 breadth or larger by a half. The length varies 

 between 12 u. (occasionally less) and 30 a., fre- 

 quently 16 — 22, the breadth between 7 and 14 p.. 

 The lower cells of each of the said cup-shaped 

 layers appear longer, rectangular, the uppermost 

 ones shorter or often almost square, as in most 

 of the Lithothamnia forming similar layers. The 

 cells of the perithallium are squarish or rectangular, 

 frequently with thicker walls than the former, 

 6 — 14 u.. long and 6 — 9 ij., broad; fig. 18. 



The organs of reproduction are unknown 

 in the species in question. However, as remarked 

 1. c. the plant must be considered to be a true 

 Lithothamnion , judging from a solitary cavity 

 resembling an emptied conceptacle of sporangia, 

 which appears just below the surface in a section of a branch. This supposed conceptacle is 

 about 550 u.. in diameter by a height of about 220 y.., and is overgrown with a few layers 

 of cells. It is however to be observed that the walls of the conceptacle have partly been torn 

 away during the grinding of the section; fig. 18. Therefore, it cannot be realized whether it 

 actually represents the said organ, although there is every probability it does. In another, but 

 fragmentary, section of a rather young specimen, in habit and structure fully resembling the 

 species in question, are to be found a few other overgrown conceptacles, which also seem to 



Fig. 18. Lithothamnii um A. Web. et Fosl. 



Part of a median section of a braDch, with a supposed 



conceptacle of sporangia overgrown; x 72. 



