82 THE BOTANICAL MAGAZINE. lvoI. xxxm. No. sss. 



cyathiform compartment at the base (Plate 1, fig. 13). 



As long as the sporelings remain in single rows of cells, 

 they vary very little in their thickness which measures 10-12 ft. 



Ill the next stage, the cells are divided into two b}' a 

 median line, resulting in two i-ows of cells. In most cases the 

 apicid cell, and frequently the basal cell too, remains undivided. 

 Successive divisions in transverse and longitudinal direction take 

 place in each cell as to form an oblong-ovate, monostromatic 

 blade. (Plate 1, fig. 12 g-i.). 



In this stage, the lowermost one or two cells of the blade 

 begin to elongate downwards to form new rhizoidal strands. 

 The strands traverse through the membrane of the first-formed 

 rhizoid and many furcate as their tips reach the substratum. 

 Some of the later-formed rhizoidal strands traverse downwards 

 through this compartment. In a more advanced stage of the 

 development of the blade, the atrophied rhizoid is no more to be 

 seen. The root of the plant now consists of numerous rhizoidal 

 strand issued from the lower cells of the blade. (Plate 1, fig. 

 14). Such sporelings as nearly agreeing with those just des- 

 cribed were observed by Derbes and Solier'\ by Bornet and 

 Thuret"\ and by Okamura''^ 



Okamura's illustration of the development of Porphyra is 

 of the sporelings found in autumn. In his illustration, the 

 basal parts of the sporelings are not satisfactorily shown. His 

 material appears to have been the sporelings grown on the twigs 

 planted for the purpose of cultivating the plant. In such spore- 

 lings, the basal parts are among the filaments of various micro- 

 scopical algae, such as Ulotorix, Lynghya, Calothrix, etc., and 

 it is not an easy task to pursue their structure in detail. Rosen- 

 venge'^ delineates a sporeling of P. umhilicaUs growing upon 

 Nemalion multifidum. His specimen had three basal cells issuing 

 the rhizoidal strands, those from the upper two traversing 

 through the wall of the lowermost one. In the material on the 

 cement-block, the rhizoidal part may be clearly seen by treating 



1) DkubEs et Soliek: M^ni. s. quelq. p. dc lu Phys. ilcs Alg., V\. XVI, fig. 12. 



2) Bornet et Thuret: Eludes Phycologiques. PI. XXXI. 



3) OkamurA: Kaisugaku Hanron, PI. X. 



4) RosENVENCiE: Marine Algae of DeniiKirk, I'iirt I, p. 6-1 fig. C. 



