12 NATURAL HISTORY SOCIETY 0¥ DUBLIN. 



spores, as monoecious species, whose male sexual organs reach their full" 

 completion only after separation from the mother plants, just as indeed 

 the pollen-tube likewise represents a sexual organ, developing itself 

 outside its place of formation; and, regarded from this point of view, 

 these dwarf forms would only possess the value of sexual organs. On 

 the other hand, starting from the more developed forms, which possess, 

 in their foot-cell, a true vegetative cell, we might with as good reason 

 interpret these dwarf forms as independent male plants, for which 

 also the nature of the androspore, which is indeed a true, though it be a 

 smaller zoospore, seems to speak. According to this, the species belong- 

 ing here would form a division of the dioecious group, in which the 

 males would be regularly smaller than the females ; and we might distin- 

 guish between a dioecious type with a similarly formed male and female 

 plant and a dioecious type with a dwarf male. Manifestly, however, 

 there is expressed in this equivocal behaviour a condition fluctuating 

 between the monoecious and dioecious type, which presents itself to us 

 as a middle stage and a connecting link between these two usual sexual 

 conditions ; and this the more distinctly, if we once more review the 

 entire series of these dwarf forms, and compare them with the deve- 

 lopment of the male sexual organs ' of the purely monoecious and dioe- 

 cious species. 



" In the first place, as already remarked, the antheridium-cells in 

 which special mother -cells and antherozoids directly originate, appear 

 not at all distinct in structure and development from the smaller 

 mother-cells of the androspores, which occur in the species which pos- 

 sess the dwarf male plants. Also the androspores themselves, in struc- 

 ture and size, form an unmistakeable, extremely noteworthy middle 

 stage between zoospores and antherozoids, as indeed generally in this 

 Family the antherozoids and zoospores are morphologically distin- 

 guished in only unessential peculiarities, in spite of their value physiolo- 

 gically so distinct. 



" Further, from the monoecious species there is an almost impercepti- 

 ble transition to those species with dwarf males, whose androspores 

 develope antherozoids directly in their interior. From these most sim- 

 ple dwarf forms an uninterrupted series leads to the more developed, 

 with imperfect and perfect foot-cell, distinct from the antheridium, 

 which finally in its developed form may be rightly regarded as a" com- 

 plete though minute male plant, directly approximating to the purely 

 dioecious species, in which, indeed, likewise in some species the males 

 are more slender than the females. 



"Hence my previously expressed view, that those species with dwarf 

 males represent a condition of the sexes which holds a middle place 

 between the monoecious and dioecious type, appears to me fully justified. 



" JSTow, the essential character of this hitherto not distinguished con- 

 dition, which includes all subordinate cases, resides, however, in the cir- 

 cumstance that the male plant, in certain cases reduced to a simple male 

 organ, proceeds here ordinarily from the development of a propagative 

 cell, which is generated in the female plant in an asexual manner. 



