and its relation to that in the Animal Kingdom. 455 



Mosses are gonidia of a nurse; those of the Ferns and Equiseta 

 correspond to the hermaphrodite or unisexual flower-buds of the 

 Phanerogamia, or rather to the rudiment of these^ their primary 

 cell — separating from the mother-plant before their development 

 into flowers; the megaspores of the Lycopodiaceae and Rhizocarpea 

 stand in the same relation to the female flowers of the Coniferae ; 

 the microspores, lastly, to the pollen-grains of the Phanerogamia, 

 to which latter may be applied the name 'spores' with the same 

 right as to the previously enumerated structures, since the term 

 can relate to nothing further than individualized cells of similar 

 outward character and corresponding mode of formation, which 

 play a part in the propagation of plants. And yet with so vague 

 a definition we should already take away the name from the 

 spores of the Algse ! 



We have already given the reasons for our opinion of the im- 

 port of the spore of Chara. From it, after a long pause, directly 

 proceeds a sexually-potent thallus. In this respect it corresponds 

 to the embryo of the Phanerogamia. Its envelope, the sporan- 

 gium, as Schacht has already rightly observed*, corresponds to 

 the archegonium of the higher Cryptogamia. 



The value of the spores and spore-capsules of the Floridecs 

 must be decided by future researches. 



In the Fucacece (so far as is known at present) the segmental 

 spore, as primordial cell, corresponds to the unfecundated ger- 

 minal vesicle of the higher divisions of the Vegetable Kingdom. 

 From it is directly produced the sexual plant. 



Among the Freshwater Algce, Vaucheria is most allied to the 

 Fucacese. A cell preparing germinal substance opens at its 

 apex, and from this moment its membrane becomes a sporan- 

 gium, and its contents a primordial cell corresponding to a ger- 

 minal vesicle. After fecundation it presents itself, enclosed by 

 a special membrane, as a completed propagation-cell — embryonal 

 cell, which, after a long rest, is developed directly into the per- 

 fect plant. 



The fecundation of Spharoplea (and Achlya) takes place in a 

 similar manner. The only distinction here consists in the spo- 

 rangium containing a number of primordial spore-cells, which, 

 as in FucuSj are all fecundated ! 



In SphcBroplea, in Bulbochcete and Coleochate, the perfect spore 

 presents itself as a nurse, whose dissimilar progeny (zoospores) 

 become perfect Algse. We here meet with retrogression to an 

 asexual multiplication at a very early epoch of life, and it might 

 appear questionable whether we ought to consider the said pro- 

 cess merely as such, or as a true alternation of generations, 



the correct criterion for determining the value of a structui*e; we must 

 regard the function as, above all, decisive on this point. 

 * Pflanzenzelle, p. 400. 



