48 Dansk Botanisk Arkiv, Bd. 2. Nr. 2. 



cells and are much ramified. They enclose the narrow, basal 

 part of the thallus and form together with it the flattened disc 

 by means of which the plant is fastened to the substratum. 



Groups of hairs in concentric rings occur upon both sides 

 of the thallus (Fig. 29 a) but mostly upon the upper surface. 

 The tetrasporangia are disposed mostly in regular concentric 

 rings; these are rather regularly arranged in such a way that 

 each series of tetrasporangia has a row of hairs on each side 

 (Fig. 30). 



The groups of tetrasporangia are not covered by any indu- 

 sium (Fig. 29 a, b); the tetrasporangia originate each from a 

 single surface cell (Fig. 29 a) as already described by Nägeli and 

 Reinke for Padina Pavonia. The surface cells are vaulted up- 

 wards and when they have grown somewhat they are divided by 

 a horizontal wall near their base into two cells, the uppermost 

 being the sporangia. These are spherical or pyriform of shape 

 and are opened by a large hole at their apex (Fig. 29 a). 



In referring this form to Kiitzing's Zonaria gymnospora I 

 must point out that compared with the figure of Kützing it 

 differs considerably ; for instance the transverse section of the 

 thallus with tetrasporangia (1. c, pi. 71, II, fig. c) does not quite 

 agree with what I have found and that the plant near the base 

 should be composed of so many layers of cells as shown in fig. d 

 is quite in contradiction to my observations ; I only have found 

 3 layers of cells though surrounded certainly by a thick layer of 

 rhizoids. Yet I want to point out that if we look more carefully 



at Kützing's figure b, representing 

 surface view of thallus with tetra- 

 *^^^;^^ ;x sporangia, we will find that these 



are drawn in groups and each of 

 these groups is surrounded by a 

 common line, suggesting an indu- 

 sium, compare my figure 27 d of 

 P. Sanctæ Cruris; in the correspon- 

 ding figure of P. Antillarum (Kütz., 

 Tab. Phycol., pi. 12, fig. lid) such a 

 common ring is not present. How 

 J.f?°- T P " dina gymnospora ^^ stfmd ^ ^^ ig 



Kutz. Vickers. Part of the J 



thallus showing the mutual ar- not easy to say without access to 

 rangement of the series of hairs original specimens, but in any case 

 and tetrasporangia. Kützing in the diagnosis of Zonaria 



(About Vl-i-.l). gymnospora says: "sporis nudis". 



