No. 3] REMARKS ON NORTHERN LITHOTHAMNIA. 85 



As to structure the species in all essentials corresponds with 

 Ph. polymorphism. The hypothallium is often strongly developed, 

 and the cells are in part longer than those of the said species, 

 14 — 30 fJ- long and 6 — 12 fi broad. The perithallic cells resemble 

 those of Ph. polymorphism both in shape and in size. 



The reproductive organs of this species are not yet sufficiently 

 known. The form torosa now and then bears numerous concep- 

 tacles of sporangia. They are a little prominent, i. e. the roof is 

 at the level of or a little above the surface of the plant, with 

 elevated annular border and mostly with but a small portion of 

 the central part impressed, 250 — 400 \i in diameter, and the roof 

 being frequently perforated only by a comparatively small number 

 of muciferous canals. These conceptacles, however, do not seem 

 to be normally developed. I have examined a considerable number 

 of them without finding any sporangia. In several conceptacles, on 

 the other hand, I have found small animals which attack the germs 

 of the sporangia, and which by growing and perhaps occurring 

 in considerable numbers seem to bring about a raising of the roof 

 of the conceptacle. The roof is of a looser consistency than usual, 

 and is apt to decay. The conceptacles sometimes bear similar 

 disc-shaped and easily decomposable formations of tissue as those 

 mentioned under Ph. Icevigatum. Overgrown conceptacles I have 

 not seen in this form, but in a vertical section of the perithallic 

 layer I have found some which have been effaced by local forma- 

 tions of tissue after the dissolution of the roof. The conceptacles 

 of cystocarps are convex or subhemispheric, become decorticated, 

 and are finally often scarcely rising above the surface of the frond ; 

 they are of about the same diameter as the conceptacles of spor- 

 angia. However, I have never seen them cup-shaped, as is often 

 the case with Ph. polymorphism and particularly Ph. Icevigatum. 



In the form ocellata the conceptacles of sporangia are fre- 

 quently of the same shape as those of Ph. polymorphism, but 

 generally a little larger, or 250 — 400 fi in diameter, and the roof 

 is traversed with 50 — 70 muciferous canals. They contain four- 

 parted sporangia which are 120— 135 /* long and 45 — 60 jx broad. 

 There are, however, also such conceptacles as those mentioned 



