i'"">l Skottsherg: Pylaiella Postelsiae loo 



prostratf* thrfads; in a few cases I have seen them forked quite near 

 their base. The lonir branches remain simple or carry short ones. 

 The lowest fM'lJs difTcr- fn xii Hie rost by their thicker walls. They are 

 two to four- times as long as wide, measurinfj: 12 to 15/x across. From 

 these cells scattered hyphae branch off, growin? downwards and serv- 

 ing, as usual, to fix the tufts better fpl. 19, fig. 1 ). Thon follow shorter 

 and slightly wider cells. ir)-20/x across. All the lower cells are quite 

 eylindrical : nii\y hi^dier iij) ;i sli^dit fonstrir-tion at the sopta can be 

 noticed. In Vi-vy youni; fihinii-nts 1lief<,' is litth; of no difference be- 

 tween different parts, hut as they become mature lin' long and thin 

 basal cells, which do not divide any more, become more obvioas. The 

 meristematic part is situated near the base, but generally does not 

 form a narrowly circumscribed zone. In the long filaments we observe 

 scattered places where the cell division is more active than in others. 

 This is the same mode of growth as in other Ectocarpaceae. 



The erect filaments frequently remain quite unbranched, or. when 

 they have reached a considerable length, give off pairs of .short branch- 

 lets under an angle of 60-80°. Saunder-s sp(-aks (p. 40) of two forms 

 of this plant, one branched, one unbranched; but filaments wnth and 

 without branches occur mixed together on the same individual (pi. 17 j. 

 The l)ranches occui- in I'emihir pairs and these are separated Ijy long 

 stretches of unbranched cells. It happens that only one branch of a 

 pair is developed (pi. 19, fig. 2). Two or three times I have seen the 

 cell carrying a pair of l)ranches divided by a longitudinal walP 

 (pi. 17). but otherwise the sterile filaments remain strictly monosiph- 

 onous. The short branches never branch again. ;ind I have never seen 

 one of them develoj) into a long filament. Thus there is one generation 

 of loi]g and one of short branches, which gives to this alga a very 

 characteristic appearance. I have not found any hairs. 



The cells contain numeroiLS chromatophores in the shape of small 

 round disks, as in so many other Phaeophyceae (pi. 10. fig. 3). 



Only plni-iloeidar sporangia are known. As a rule, the formation 

 of sporangia begins when the filaments have attained a considerable, 

 perhaps their maximum, length. But it happens, in this species as 

 in many others, that a young and still very short filament may become 

 fertile fpl. 19, fig. 1). The divisions begin in the apical part of the 

 thread and progress in basipetal order. This is easily understood 

 from plate 17. Generally all the cells, except those in the l)asal part. 



1 Possibl.v in these cases the coll in question was about to form spores, which 

 otherwise never happens. 



