Sept. II, 1879] 



NATURE 



463 



PROF. DODEL-PORT ON THE FERTILISATION 

 OF RED SEA WEEDS BY INFUSORIA 



TN a recent number of the excellent periodical /Cosmos, Dr. 

 ^ Dodel-Port, the eminent Zurich botanist, has published the 

 results of a series of observations made by him regarding the 

 part played by some infusoria in the fertilisation of a certain 

 species of red seaweeds or Florideos, viz., Polysiphonia subulata, 

 T. Ag. The paper is of biological importance, since it forms, as 

 far as our knowledge extends, the first record of a possible partici 

 pation of animals in the fertilisation of cryptogams, which in itself 

 seems an interesting parallel to the relations existing between 

 insects and phanerogams. We have pleasure, therefore, in 

 presenting our readers with an abstract, the illustrations for 

 which have been placed at our disposal through the kindness of 

 the author and of the publishers of Kosmos. 



In previous numbers of the same periodical Dr. Hermann Miiller 

 had sketched the history of the evolution of the floral world and had 

 shown upon what basis rests the entire relation between flowers 

 and insects. This basis is the passage from a state of things in 

 which the male cells discharged their products in a medium of 

 water to that in which this event took place in the dry atmosphere, 

 which transition period occurred at the upper boundary of the 

 cryptogamic flora of prehistoric times. 



In almost all cryptogams, which are not agamic, the contents 

 of tie male sexual cells are actively movable ; when they leave 

 the male cell they move freely about in the water by means of 

 vividly oscillating cilia. They therefore possess the faculty of 

 moving to the distant female organ, and there to complete ferti- 

 lisation. In the case of phanerogams, the independent mobility 

 of the poUen'bodies has become an impossibility. To effect the 

 union of pollen-grains with that particular part of the female 

 flower which is destined to receive them, in most plants some 

 external agent must interfere. In many cases, specially in the 

 lower regions of the floral world, the wind, gravitation, or both 

 together, are the agents in question ; in the majority of the 

 higher phanerogams, insects, or occasionally other animals, 

 undertake the conveyance of the pollen. 



Now there are a great number of cryptogams, in which the 

 contents of the male cells which are emptied into the water do 

 not possess the faculty of independent motion, as they are not 

 endowed with cilia, and are therefore dependent on the action of 

 external forces for their locomotion. To these belongs the great 

 and highly differentiated order of so-called red seaweeds or 

 ■f loridete, chiefly marine plants which vary much in form and 

 colour, and which no one who has ever attentively observed on 

 the sea-coast will ever forget. Their antherozoids, which are 

 generally spherical, are discharged into the water as motionless 

 cells, and are yielded up to the play of currents in the same way 

 as in our anemophilous phanerogams, the pollen grains pass as a 

 dust into the air, and are moved to and fro by the winds. There 

 are many analogies between Florideoc and higher phanerogams, 

 regarding their sexual conditions. Thus, amongst the former we 

 find many species which are dioecious, similar to the lowest 

 phanerogams amongst gymnosperms, and to others of higher 

 order. The chances for fertilisation in their case are therefore 

 quite similar to those applying to dicccious phanerogams. Often 

 the male plants grow at a considerable distance from the female 

 plants of the same species. In the spring of 1878 Dr. Dodel- 

 Port, during a series of microscopical examinations of the red 

 seaweeds of the Adriatic, extending over four weeks, found only 

 female and agamic (tetrasporous) specimens of Polysiphonia 

 subiilata, T. Ag., and looked in vain for male specimens, of 

 which only at the end of his investigatisns he could obtain a 

 few. Their respective localities of growth were evidently con- 

 siderably apart, and yet at all times Dr. Dodel-Port found female 

 specimens in all stages of fertilisation. The spermatozoids 

 discharged by the male plants therefore found their way to the 

 distant female plants in spite of their own immobility and general 

 passive behaviour. The sea-water must therefore have frequently 

 been in vivid motion. 



These facts being ascertained, the thought easily suggested 

 itself that possibly animals might take part in the fertilisation, 

 particularly as there is never a want of small marine animals 

 roaming about in the Floridea: forests, such as infusoria, Crusta- 

 cea, annelids, starfish, &c. But what particularly attracted Dr. 

 Dodel Port's attention was the regular occurrence of innumerable 

 bell-shaped animalcules ( Vorlicella) on the shrub like branches 

 of Polyiiphonia subiilata. In the course of closer investigation 

 of the phenomena of fertilisation in the female organ, during 



and after the adherence of the antherozoid with the trichogynei 

 Dr. Dodel-Port eventually arrived at the full conviction that in 

 the case of Polysiphonia the little Vorticellas facilitate the con- 

 veyance of the antherozoids to the trichogyne, and that they act 

 according to a natural law in the same way as do the pollen- 

 collecting bees when by visiting the willow-catkins they assist at 

 their fertilisation. The investigation of the sexual conditions of 

 Florideae is as yet in its infancy ; it is to be hoped that more 

 numerous researches in this direction will shortly be made, and 

 possibly relations may be found to exist between other species of 

 this order and certain animals similar to those discovered by Dr. 

 Dodel-Port in the case of Polysiphonia and Vorticella. The 

 details of the interesting relations in this case are shortly as 

 follows : — 



Fig. I represents the male reproductive organ (antheridium) 

 of Polysiphonia subulata magnified 480 times. These antheridia 

 often appear in large numbers at the upper branch-ends of the 

 male plant, laterally close to the apex which continues its growth, 

 at the spot where, in the vegetative state, young branches would 

 form. In their earliest stage the antheridia consist, like the 

 young branches, of a single row of cells. By repeated longitu- 

 dinal and lateral divisions a polycellular body is soon formed, 

 which begins with a short stem-cell (st), and which, on the side 

 furthest away from the maternal thallus- branch, is protected by 

 a forked hair (gh). 



The ripe antheridium in external appearance reminds one very 

 strongly of a maize cone ; a row of 4-6 cylindrical cells [a, a) in 

 the axis of the whole organ represent the spine of the cone, 

 while the surface is covered over by numerous antherozoid 

 mother-cells {sm, sm) representing the grains of maize. Before 

 the antheridium is ripe the latter are polyhedrical, but afterwards 

 they assume a round shape, as the drawing shows. All parts of 

 the male organ are colourless ; the antherozoid mother-cells are 

 filled by a finely granular plasma, which is soon differentiated 

 into a round body, which subsequently is discharged from the 

 mother-cell as an antherozoid {s, s). Thus within a short time 

 the ripe antheridium discharges some 400-800 ball-shaped 

 antherozoids into the surrounding sea-water. The single anthe- 

 rozoid is a little globule of protoplasm, without cell-wall or any 

 locomotive organ. In the centre of this globular primordial 

 cell a strong magnifying power shows a little nodule which 

 strongly refracts light, and round which a few smaller colourless 

 plasma granules are grouped. As it freely floats in the water, 

 the antherozoid is analogous to a pollen-grain of an anemophi- 

 lous phanerogam. 



The female reproductive organ of Polysiphonia suiulaia is a 

 polycellular carpogonium of relatively high differentiation. It 

 originates upon the female plant closely below the apex of the 

 thallus-branches, and generally there are several of them form- 

 ing successively at varying intervals from the branch-end 

 downwards. 



Fig. 2 shows the carpogoniumbearing branch-end of a female 

 specimen oi^Polysiphonia subulata. eg' is a very young carpo- 

 gonium ; eg, eg are two mature ones ; t' and t" are two tricho- 

 gynes ; Vorl. are two Vorticellse. The whole is magnified 300 

 times. 



In Fig. 3 a carpogonium {ea) is represented magnified still 

 more (480 times). Vort. is a Vorticella ; s, s are antherozoids. 

 In the mature state the carpogonium consists of three essential 

 parts, viz. : — 



1. The basal portion f (Fig. 3). 



2. The fertile spore-forming part eg. 



3. The hair apparatus t and gh. 



The basal portion consists of five tubular cells running parallel 

 to each other, of which in Fig. 3 are seen only two. Then 

 follows the fertile psrt, eg, which is an oval cellular body, 

 consisting of some 20-26 cells. A central cell, copiously 

 filled with granular protoplasm, is surrounded by a number 'of 

 irregular, peripheric cells, and awaits fertilisation, in order after- 

 wards to transform itself into the spore-forming apparatus, 

 while the remaining 19-25 peripheric cells become the case 

 of the spore fruit through further divisions (see also Fig. 4, 

 /( h). The uppermost part of the female organ is the hair 

 apparatus, which, in Polysiphonia, consists of the forked rhair, 

 gh, and the trichogyne, t (Fig. 3). The forked hair forms very 

 early \'.pon the young carpogonium, and indeed long before the 

 trichogyne is formed ; its position is always upon the true apex 

 of the whole organ, although at times it stands apparently 

 laterally from the apex. The duration of its existence and its 

 presence at the time of fertilisation (it disappears immediately 



