sph^rococcoidejE. 143 



marked, and in some specimens extend through all the 

 branching of the frond. Spores forming a chain round a 

 basal placenta, in depressed spheroidal conceptacles, which 

 are either disposed on the margin of the frond, or on leafy 

 processes issuing from it ; tetraspores grouped in minute, 

 oblong spots on the margin of the frond, or on marginal 

 processes. 



This is the most' variable, as well as the most common 

 of all the British species of Nitophyllum. In some spe- 

 cimens the divisions of the frond are almost thread-like, 

 while in others they are so broad as to approach the form 

 of Nitophyllum Gmelini. These differences arise, in a 

 great measure, from the peculiar circumstances in which 

 the plants grow, — whether on rocks or the stems of 

 Laminarim in deep water, or, as I have sometimes found 

 them, in shallow, tidal pools. The only species with which 

 this can be easily confounded is N. Gmelini, and from 

 that it may be distinguished by its darker purple colour, 

 softer texture, more distinct, longer veins and proliferous 

 margins. The texture of the frond is so delicate when 

 dry that it is apt to crack and part from the paper on 

 the least exposure to the air. Great care should there- 

 fore be taken of specimens in the herbarium. A cur- 

 tain of tissue paper gummed neatly above the specimen, 

 so as to fall over it, is the best protection that I can 

 suggest. 



Nitophyllum uncinatum. Clawed Nitophyllum. 



Frond membranaceous, without stalk or veins, divided 

 into linear lobes, whose tips are incurved. Spores in de- 

 pressed, spheroidal conceptacles, which are usually to be 

 found near the margin of the frond ; tetraspores in nearly 

 solitary sori, under the tips of the lobes. 



