402 PRACTICAL BOTANY 



1. Barren hairs, which are usually unbranched. 



2. Oogonia, bodies of relatively large size, and oval 

 form, with a thick transparent wall, and dark granular 

 protoplasm : each of these is seated on a unicellular 

 pedicel, and may be regarded as a metamorphosed hair. 



Observe in the largest of the oogonia that the proto- 

 plasmic body may be seen to have undergone division 

 into eight parts, the surfaces of separation being visible 

 as transparent lines. 



In order to follow the development of the conceptacle it is 

 necessary to cut sections from the apical region of a branch in 

 which the formation of conceptacles has recently begun : median 

 longitudinal sections will be found to be the best, since they will 

 often show a series of successively younger conceptacles leading 

 up to the organic apex. From a comparison of these it will 

 appear that the conceptacle is not a mere involution of the sur- 

 face, but that one (or in some cases more than one) cell of the 

 limiting layer shrivels, and is thrown off : that the walls around 

 it undergo mucilaginous swelling, which is probably connected 

 with the formation of the flask-shaped cavity : that the conceptacle 

 is closed until after the hairs begin to be formed from the tissue 

 lining it, when ultimately the ostiole opens to allow the escape 

 of the sexual cells. 



XI. Observations on the extrusion of the spermato- 

 zoids and ova, and on the process of fertilization in 

 Fucus must be made with fresh material, and will be 

 most successfully carried out on the coast, the best 

 season for it being winter or spring. Those who have 

 not opportunity for this may succeed in making the 

 observations on fresh material sent from the coast, 

 using a solution of Tidman's sea-salt, 5 ounces to the 

 gallon, in place of fresh sea-water. 



If specimens of Fucus serratus be kept exposed to 



