Structure of Hydroclathrus. 5 5 



the thallus continues its growth, so that the basal cells of the hairs which 

 were originally in the same plane as the epidermis have now come to lie 

 below it, and the whole structure is suggestive of a conceptacle. 



H. sinuosus is reproduced by spores contained in plurilocular sporangia. 

 So soon as a cryptostoma is fully formed the epidermal cells immediately 

 surrounding it begin to elongate, pushing up the overlying cuticle, which is 

 finally ruptured (plate XIV., fig. 3), and peels off as the growth of the cells 

 spreads centrifugally. From the appearance of many sporangia at different 

 stages of development it may be seen that each epidermal cell becomes di- 

 vided, as in the case of the hairs, by a transverse wall ; the lower of the two 

 cells, which represents the basal cell, remains unchanged, while the upper 

 one divides transversely. Of the two cells thus formed the lower one divides 

 longitudinally into two, the protoplasm of each half going to form a spore, 

 while the upper half again divides transversely, and the same process of 

 division takes place, with the formation of two more spores. Growth con- 

 tinues until from twelve to sixteen spores have been produced (plate XIV., 

 fig. 4). Of the sporangia forming a sorus, those immediately surrounding 

 the cryptostoma come to maturity first, and the spores are liberated; what 

 becomes of them afterwards it is impossible to determine unless growing 

 plants can be examined. After the liberation of the spores the sporangia 1 

 walls gradually disappear, and the basal cells originate a new growth. 

 They again elongate, and each is divided into two parts by a transverse 

 wall ; the lower half remains unchanged, and the upper one grows into a 

 long, club-shaped paraphysis (plate XIV., fig. 5), the contents of which, in 

 spirit material, are entirely concealed by a dark-brown colouring substance. 

 In a young paraphysis this is distributed evenly all over the cell ; in older 

 ones it appears to be collected into small globules, but how much of this 

 appearance is due to the method of preservation it is impossible to say. 

 While the basal cells nearest the cryptostomata are giving rise to 

 paraphyses, those farthest away are still producing sporangia, and, as the 

 growth of the sporangia spreads radially from the cryptostomata, so also 

 does that of the paraphyses, until finally all the sporangia have disappeared, 

 and there are scattered over the thallus in the place of the sori groups of 

 dark-coloured paraphyses, each having a central cryptostoma. The hairs 

 of the latter are shrunken, and the cells have lost their contents, but they, 

 together with the paraphyses, appear to persist throughout the remaining 

 life of the plant. It is of interest to note here slight differences in the 

 structure and appearance of the plants coming from different localities 

 (cp. plate XIV., figs. 3 and 6). Thus the form of the inner cells of the thallus 

 is round in the plants coming from Madras, and more elongated in those 

 from Anguilla. Again, in the plants coming from Anguilla the crypto- 



