478 Mr. Valentine on the Development of the Theca, 



iu every essential particular. In support of an opinion so opposite to any 

 hitherto proposed, I offer the following evidence*. 



The analogy of the development of the sporules to that of pollen is very 

 striking even to a superficial observer, and has not escaped the notice of 

 botanists. A section of the anther of the common garden variety of Primula 

 vulgaris, taken from a bud when about the size of a small pin's head, exhibits 

 a structure which may be compared to a section of the theca of Polytrichum. 

 In the former we find an axis of dense tissue (the connectivum) surrounded 

 by the cuticle. This axis is not central, but placed nearer to the cuticle, on 

 the back of the anther, and may be considered as the columella ; whilst the 

 cuticle will represent the theca. A separation of the tissue gradually takes 

 place, in four distinct points, nearly at equal distances from the axis. As the 

 axis is not centrical, these points lie towards the front of the antlier. Between 

 each of these points the cuticle is furrowed longitudinally, so that the section 

 has somewhat of a quadrangular figure. The theca of Polytrichum merely 

 differs from this in having a complete separation of its tissue all round the 

 axis instead of in four points only. The spaces caused by the separation (not 

 dissolution) of the tissue, gradually enlarging, form the cells of the anther, in 

 which the viscid secretion takes place. This secretion is afterwards converted 

 into pollen, in a manner similar to that in which the sporules are formed. 

 When the anther is nearly ripe, a still further separation of the tissue takes 

 place, and the four cells become two. When perfectly mature, these cells 



* Since this paper was read, Mr. Brown has called my attention to a memoir by Professor Hugo 

 Mohl (see Flora, No. 5, February 1S33, p. 65, et seqq.), in which the same views are advanced and 

 supported at considerable length. 



I may also mention that on the second evening of the reading of this paper Professor Agardh of Lund, 

 who happened to be present, informed me that he had maintained a similar view to the one above as to 

 the nature of the sporules of the Alg<e, in a work which he had published, but which had not found its 

 way into this country. [The work here alluded to is probably the second volume of the Lehrbuch der 

 Botanik, of v^hich a German translation appeared at Greifswald in 1832.] 



I am aware that Mons. Palisot de Beauvois endeavoured to prove that the sporules were pollen. 

 He maintained that the sporules impregnated the seed (which he fancied he had discovered), like the 

 pollen of Phsenogamous plants ; — a view the very opposite to the one proposed in this paper. 

 Mr. Brown has long since (Linn. Trans, x. p. 314.) pointed out the error of M. de Beauvois. 



