EUPHYCOPHYTA 227 



from which the adult plant grows. The full hfe cycle of P. umbili- 

 calis can be represented as in fig. 124. 



The genus, which goes under a variety of different common 

 names in the various countries, is much used as a food (see p. 450). 

 The plants normally occur on rocky coasts towards high-water 

 mark. Haploid chromosome nimibers of 2, 3 and 4 have been 

 reported and further counts are clearly required. 



EUFLORIDEAE 



The plants consist of branched filaments, or are compact pseudo- 

 parenchymatous or membranous thaUi with the uniaxial or 

 fountain type of construction. Fundamentally they are heterotri- 

 chous though this condition is lacking in many. Growth is normally 

 from one or more apical cells and plasmodesmae are present. The 

 carpogonium is usually highly speciaHzed and only one spermatium 

 is produced from each antheridium. The zygote nucleus commonly 

 passes into the special auxiliary cell and after fertilization there is 

 produced a parasitic phase, the carposporophyte, producing carpo- 

 spores. This is nearly always diploid and then the carpospores give 

 rise to an asexual generation reproducing by means of tetraspores. 



Nemalionales 



A primitive order in which the vegetative structure is both uni- 

 and multiaxial. There are no true auxihary cells in many genera 

 {Batrachospermuniy Nemalion) whilst in others the so-called auxihary 

 cell may be largely nutritive {Galaxaura). In the majority of the 

 genera only haploid plants are represented in the life cycle, but 

 in the genus Galaxaura there is distinct alternation of genera- 

 tions, and in the Bonnemaisoniaceae some extremely peculiar life 

 cycles^ have been recorded. 



There are eight families in the order and as we come to know 

 more about them it may become desirable to spht the order. The 

 Chantransiaceae, Batrachospermaceae, Lemaneaceae, Naccaria- 

 ceae and Bonnemaisoniaceae are all uniaxial. The last-named family 

 differs from the others in respect of some remarkable life cycles 

 (see under Asparagopsis, p. 230), and also in possessing cystocarps 

 of distinct shape with gametophytic walls. The Thoreaceae, Hel- 

 minthocladiaceae and Chaetangiaceae are of multiaxial construc- 



^ Magne (1961) has recorded one also for Nemalion helminthoides. 



