6 Splachnidium rugosum. 



are chiefly confined to the region surrounding the ostiole, only a few 

 remaining between the sporangia. Conceptacles which may be said to 

 have passed their maturity contain sporangia which have lost their 

 contents, only the clear hyaline walls remaining (plate III., fig. 5). The 

 sporangia are ruptured irregularly at the apex, and strongly resemble 

 those of the Laminariace& (cp. plate III., fig. 6, e, and fig. 8). They are 

 persistent, and in this offer a contrast to the empty oogonia of the 

 Fucacece, which disappear after a short time. 



STRUCTURE AND DEVELOPMENT OF THE SPORANGIUM. A 

 sporangium arises as a papillose protuberance of one of the lining cells 

 of the conceptacle. This elongates and enlarges into a club-shaped body, 

 having its base sunk between the adjacent cells of the wall of the con- 

 ceptacle, and it becomes completely filled with a dark-coloured pro- 

 toplasm. When the sporangium has attained its full size, the protoplasm 

 becomes differentiated into spores, the differentiation proceeding simul- 

 taneously throughout the whole sporangium. The spores do not entirely 

 fill the cavity of the mature sporangium, the wall of which gives the 

 cellulose reaction when treated with iodine and sulphuric acid. 



It should be noted that there is no division of the original papillose 

 protuberance into two cells, forming stalk-cell and sporangium respectively. 

 In all Fucacece, on the other hand, the oogonium is supported by a pedicel 

 cell, which is cut off from the protuberance in the very beginning ; only in 

 Pelvetia, so far as is known, is this cell somewhat obscure, owing to the 

 fact that it does not elongate to form a stalk as in other cases. 



The sporangium is unilocular. Treatment with eau de javelle dissolves 

 the undifferentiated protoplasm or the spores within, but leaves no trace of 

 an intrasporangial network. Reinke* has shown that similar treatment of 

 the multilocular sporangia of some other Algae brings out a well-defined 

 intrasporangial network. That there is no inner membrane enclosing 

 the spores may also be demonstrated by the action of eau de javelle. 



The spores when liberated by pressure from a sporangium of average 

 size are found to number from 500 to 600 ; they measure approximately 

 -2^0 mm. in diameter. It may be noted that this is also the average 

 diameter both of an antherozoid of Fucus serratn.s^ and of a zoospore of 

 the Laminar iacecz. It is calculated that the volume of an oosphere of 

 Fucus sermtus is 20,000-30,000 times as great as that of an antherozoid 

 of the same plant. These figures therefore express the ratio between the 

 volumes of the oosphere of Fucus serratus and of the spore of Splachnidium 

 rugosum. 



* Reinke, Atlas deutscher ATeeresalgen, p. 49, tab. 32, fig. n. 

 t J. Thuret, Eludes Phycologiques. 



