182 INTRODUCTION TO CRYPTOGAMIC BOTANY. 



locladia articulata also, which is one of the most frequent 

 species on our coasts, deserves notice, from the elegant chains 

 of elliptic articulations of which the frond is composed, which 

 never fail to excite the admiration of those who meet with 

 well -grown specimens, and it has the advantage of preserving 

 the greater part of its beauty when dry. Glceosiphonia is 

 remarkable for its gelatinous frond. It is one of the most 

 beautiful Algse of our coasts, and rather rare, though widely 

 diffused. 



4. Rhodymeniace^, Harv. (RJiodymeniece, J. Ag.) 

 Inarticulate, membranaceous, cellular ; nucleus in an external 

 conceptacle, simple or compound. Spores at first in moniliform 

 threads, at length conglobated. 



157. The froud, in the Algte of this division, is inarticulate 

 and mostly flat, though varying considerably in form, being 

 sometimes cylindrical. The colour is in some of a dull reddish 

 purple, while in others it is of a fine blood-red. The 

 nucleus is lodged in globose conceptacles, and the spores are 

 produced within the joints of moniliform threads, and at 

 length are dispersed within the sac, without any definite 

 arrangement. Occasionally the moniliform threads of the 

 nucleus are disposed in separate chambers by means of threads 

 proceeding to the walls, as we shall see again, in the Geli- 

 diacece. The endochromes of certain privileged joints of these 

 threads suffer repeated division, and on the absorption of the 

 walls of the parent cell are dispersed without order in the 

 common cavity, or in the partial chambers. It is obvious that 

 at an early stage of growth they could not be distinguished 

 from Algge, with ordinary moniliform threads. The spores 

 themselves, according to their number, will either retain their 

 original form, or become angular, from mutual pressure. An 

 accurate study of the fruit is so much the more necessary, 

 because the frond, as regards structure, is often so exactly like 

 that of analogous forms as to defy the most practised eye. 

 This is truly a great inconvenience to the student ; but if a 

 really natural system is to be adopted, depending not upon 

 external resemblance merely, but upon intimate structure, such 

 difficulties will constantly arise. Amongst the patellEeform mol- 



