SECT. IT. RHODOSPERMEJE. 227 



spores. After a time they come to rest, attach, themselves 

 to some object, and begin to grow. The walls of the 

 cells which have thus discharged their endochrome in 

 the form of zoospores, remain as colourless spots on the 

 frond. The whole colouring matter of a portion of the 

 frond may escape as zoospores, leaving behind it nothing 

 but a white membrane. With a microscope, this process 

 may sometimes be observed in all the different stages of 

 its progress. 



Every full-grown Ulva has its own precise and definite 

 form, but whatever that may be, the young plants on 

 their first appearance from the shore are in all respects 

 similar to Confervas ; the top cells soon divide, and a 

 plane or sac-like frond is formed. 



Certain TJlvas, which have a yellow tint, produce small 

 zoospores with only two cilia, but in the Ulva bullosa 

 and the Ulva latissima four zoospores are produced in 

 the same cell, each having four cilia. The same fructi- 

 fication prevails also in the purple Ulvas Porphyra, 

 laciniata and vulgaris. The latter is seen in winter and 

 the early spring, covering the rocks near high water 

 mark, with its tiny bright purple lanceolate leaves. 

 Later in the season it grows into a flat narrow ribless 

 frond with a pointed end, and about two feet long, the 

 margin of the frond becoming waved and plaited as the 

 plant increases in growth. At a later period, it is seen 

 mixed with the Porphyra laciniata, which is a ribless 

 flat frond of a dull purple ; sometimes it is very thin, 

 divided or torn, and occasionally growing in a circle 

 round its root. Both forms are sold as laver. 3 



The BHODOSPEEME^E, Florideae, or Eosetangles, are the 

 most beautiful of the marine vegetation. No sea plant 

 surpasses them in delicacy and grace of form or richness 



' British Seaweeds.' By Mrs. Alfred Gatty. 

 Q2 



