AdenocystiS) Alaria and Saccorhiza. 61 



The study of the structure and development of bodies of this character 

 among the Phceophycea is, therefore, one of interest, so far as such may 

 throw light on the origin of conccptacles. In connexion with the above 

 comparison of the Laminarian with the SplacJmidian sorus, it will be 

 remembered with interest that cryptostomata occur in the Laminariaceae. 

 Through the kindness of Mr. George Brebner, whom I asked to look out 

 for them at Cumbrae, I have been so fortunate as to obtain good examples 

 of their occurrence in Saccorhisa biilbosa and Alaria esculenta. Alaria has 

 been frequently described as possessing cryptostomata. Greville* definitely 

 refers to them as ' minute pores from which issue minute tufts of filaments' 

 and Prof. Bower (loc. cit., p. 36) refers to them also in passing. I have not 

 placed myself in antagonism to these authorities on this minute point, 

 without arming myself with certainty. On plate XVI., figs. 4, 5, and 6, there 

 will be seen a surface view of the Alaria cryptostomata, a transverse 

 section of the frond showing them in a very early stage, and another in an 

 advanced stage. It will be seen that so far no pits or conceptacles are 

 formed, and in a very old Alaria frond which I have examined there was 

 at most a depression one cell deep. The Alaria cryptostomata, if I may 

 call them so, are tufts of hairs with basal growth, the cell at the apex of 

 the hair being first cut off from the epidermal layer. 



On plate XVI., fig. 7, I have illustrated the mature cryptostoma of 

 Saccorhiza bulbosa. So far as I am aware, the mature stage of these bodies 

 in Saccorhiza has not been figured before, and the reader who compares 

 this figure with that of the young conceptacle of SplacJinidimn (plate III., 

 fig. 3), while it yet bears hairs only, cannot fail to be struck by the resem- 

 blance in all respects except the persistent initial cell of Splaclinidiuin . 

 We have here, then, a body which has every claim to rank as a cryptostoma. 

 Mr. Setchell,* in his admirable paper on the life-history of Saccorhiza 

 dennatodea has figured (loc. cit., plate II., fig. 22) an early stage in the 

 development of the cryptostomata of 3". dennatodea^ which bears the most 

 close resemblance possible to this early stage of Alaria. He says (p. 202): 

 ' The first indication that a cryptostoma is forming is the appearance of a 

 shallow, saucer-shaped depression. This will be seen to be due to the fact 

 that the cells of the limiting layer in the region of this depression cease to 

 divide as actively in a tangential direction as they have been doing, or as 

 actively as their neighbours are doing. Furthermore, the cells of the outer 

 cortex immediately below this point do not increase in size either so rapidly 

 or to so great an extent as their neighbours do,' &c. This is so like what 

 happens in Splachnidium (without the persistent initial cell) as to be 



t 



* Alg. Brit., p. 25. t Proc. Amer. Acad. of Arts and Sciences, vol. xxvi. 



