EUPHYCOPHYTA I39 



form of growth is termed auxocaulous. Cladostephus also forms long 

 branches which arise in a hemiblastic manner. Since the initial does 

 not undergo any anticlinal divisions (Fig. 76, B) it is equivalent to a 

 number of initials representing laterals of limited growth. 



There is no special means of vegetative reproduction. Both uni- 

 locular and plurilocular sporangia are formed on special branchlets 

 or stichidia, which arise from the rhizoidal cortex in the internodes 

 between the whorls of vegetative branches. The different types of 

 sporangia occur on separate plants, the unilocular, which produce 

 zoospores, on the diploid generation, and + and - plurilocular 

 sporangia on separate gametophytic plants. The plurilocular 

 sporangia give rise to isogametes. 



Stypocaulaceae: Halopteris (halo, sc2i; pteris, fern). Fig. 77 



The pinnate frond arises from a distinct basal pad, the plants in 

 summer having the appearance of shaggy tufts, whilst in winter 

 the branching appears more regular as surplus branchlets are shed. 

 The inner cortex of the central axis is composed of a nimiber of 

 cubical cells whilst there is also an outer cortex of rhizoidal cells 

 (pericysts), the whole forming a pseudo-parenchyma. Since there 

 is no enlargement of the original cells Halopteris is leptocaulous. 

 Pericysts are only found in the main axis and branches of tmUmited 

 growth. Branching in Halopteris is holoblastic (cf. hair production 

 in Sphacelaria). At an early stage the branch initial cuts off a small 

 upper axillary cell. This cell is regarded as the true apical cell so 

 that the branch is really a lateral of a diminutive branch axis. In 

 some species the axillary cell may later give rise to a tuft of hairs. 



The sexual and asexual generations alternate, the former repro- 

 ducing by means of antheridia and oogonia and the latter by uni- 

 locular sporangia and zooids. The reproductive organs are borne 

 in the axils of laterals (when they must be regarded as terminal on 

 axillary shoots) or on branchlets arising from pads derived from the 

 axial initial. In H. scoparia the sori are united into spikelets, the 

 lower laterals being sterile and only the upper being fertile. Many 

 years ago an herbarium plant of Halopteris was reported with 

 oogonia and antheridia but it was not until quite recently that the 

 living material with these organs was found in New Zealand. A 

 number of species are known, especially from the South Pacific, 

 but their identification is not always easy. 



