Reproduction and Affinities of Dasyptilon 
(Ceramiaceae; Rhodophyceae ) 1 
David Erskine 2 
The genus Dasyptilon was set up by Feld- 
mann-Mazoyer in 1950, for the New Zealand 
species long known as Plumariopsis pellucida 
(Harv.) de Toni. (Although doubts as to its 
identity with Harvey’s type had been raised 
both by the New Zealanders and by G. 
Feldmann herself, the type of Ptilota pellucida 
Harv. seems conspecific, permitting ascrip- 
tion of the correct name D. pellucidum to 
(Harv.) de Toni, rather than "(Laing) de 
Toni.”) She indicated as distinctive two im- 
portant vegetative characteristics, the ob- 
liquely-dividing apical cell, and the rhizoidal 
cortication, and in addition the position of 
the tetrasporangia. However, the develop- 
ment of the cystocarp was quite unknown. 
Opportunity and incentive for its investiga- 
tion was furnished by the collection of abund- 
ant female material in March, 1949, at St. 
Clair, Otago, South Island, New Zealand, 
by G. F. Papenfuss. 
The vegetative structure of the purplish 
feathery fronds is essentially that of the 
Ptiloteae. The apical cell divides obliquely 
and alternately to left and right. Each cell of 
the filament which results produces two 
branches, the first from the longer side, one 
or two cells behind the apex (Fig. 2b); the 
second on the shorter side, one or two cells 
further back. In the vegetative shoot, the first 
branch becomes secondarily branched, the 
1 This study was carried out in the Department of 
Botany at the University of California, Berkeley. Manu- 
script received February 12, 1954. 
2 Department of Geography, University of Toronto. 
second remains simple, thus building up a 
distichous frond of alternating long and short 
branches. 
In the fertile shoot, each short branch bears 
a four celled carpogonial branch upon its 
proximal cell. This cell is, in respect to the 
main axis, pericentral, as is typical of cera- 
miaceous procarps. Apparently the carpo- 
gonial branch is produced before the sterile 
cell (rudimentary vegetative short branch) 
(Figs, la, 2b), a development which may be 
characteristic of the Ptiloteae, as it has been 
noted both by Kylin (1923) in Ptilota* plumosa 
(Huds.) C. A g. and by Suneson (1938) in 
Plumaria 3 elegans (Bonnem.) Schmitz, though 
Drew (1939) found that in the latter either 
might be produced first. If no carpogonium 
of the shoot is fertilized, the short branches 
resume growth to their normal character (Fig. 
la). In event of fertilization, further growth 
of the shoot above the fertile axial cell is 
checked by diversion of its nutriment to the 
gonimoblast. The primordial long branches, 
one to three cells in length, produce a ter- 
minal hair and cease growth (Fig. 2a, d). 
Apical development ceases in the short 
branches when they are composed of only the 
pericentral and (sometimes) a terminal sterile 
cell. The whole apex of the shoot may be 
deflected laterally by the growth of the cysto- 
carp and becomes overtopped by several 
vigorous involucral branches arising from the 
axial cell below the fertile one. Occasionally 
3 Generic names proposed for conservation. 
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