294 MacMillan: Observations on Nereocystis 



of the paraphyses as they elongate space is afforded the sporangia' 

 for their development. In half-mature sori in which the para- 

 physes were 20 mic. in height the sporangia could be seen as 

 elhpsoid cells about half as long and of quite different shape from 

 the already club-shaped paraphyseal cells. In mature sori, how- 

 ever, when the spores have been formed in the sporangia the dif- 

 ference in the height of the two cells is not so great and the para- 

 physes overtop the sporangia by but about 10 mic. or even less. 

 The distal end wall of the paraphyses is thickened as in other 



ft 



genera of the same subdivision of the family. 



Free zoospores have not been seen but sporangia ready to open 

 have been found and the spores appear as hyaline cells close to i 

 mic. in the short diameter and a very little longer transverse to 

 this. The sporangia doubtless open at the tip to discharge the 

 hundred or more spores contained in each. The end wall of the 

 sporangium, like that of the paraphysis is often considerably thick- 

 ened. I am able to confirm upon Nereocystis material the results 

 ofThuretwho noted in 1850 the separation of a thin cuticular 

 pellicle from the surface of sori in ScytosipJuvi, Laminaria and some 

 Fucaceae. This pellicle retains the partition-markings of the 

 original epidermal cells quite as figured by Thuret for LiWiinaria 

 sacchanna and Scytosiphon loincntarius. The e.xact manner in 

 which this pellicle is separated does not yet appear to be clearly 

 understood, nor am I able to say more about it at this time than 

 that the wall of the soral surface when young seems to be lamel- 

 lose and the separation of the cuticular pellicle seems to take place 

 by the dissolving of one of the lamellae. Before the separation a 

 {dwr very small bodies, red-stained in aniline-safranin preparations 

 are seen lying against the inner face of the distal wall of each 

 paraphysis. It is possible that they assist in the secretion of the 

 thick pellicle which is finally sloughed off. Sometimes two trans- 

 verse divisions precede the forpiation of the paraphysis in which 

 case two layers of floor-cells are produced in the sorus. One or. 

 two jointed paraphyses have been seen. The paraphysis seems 

 never to consist of more than two cells and the two-celled condi- 

 tlon is extremely rare. ^ 



I am under obligation to Miss Josephine E. Tilden for putting 

 at my disposal an abundance of carefully preserved material and 



