440 HOFME1STER, ON 



tainty in the different species as to the sexual function of 

 the reproductive cells which are cast off from the organism 

 itself, viz., the spores. In these orders species nearly allied 

 to one another are partly mona?cious and partly dioecious. 

 Certain species amongst theCharae,Muscineae, the Ferns, and 

 the Equiseta,* produce both kinds of sexual organs, arche- 

 gonia and antheridia, upon the same individual of the genera- 

 tion preceding impregnation : the latter are always produced 

 before the former. In other Characeae, Muscineae and 

 Equiseta, the male and female sexual organs are distributed 

 upon different individuals a separation which is very com- 

 plete in certain species of mosses, and not in others. The 

 spores from which, in the Characese, Muscinae, and Equi- 

 seta, diaecious prothallia are developed, exhibit no indica- 

 tion of the sex of the individual to be produced from them. 

 But there is often a marked difference in the complete form 

 between the male and female individuals : the former are 

 much smaller than the latter ; they are dwarfish. Extreme 

 instances of this are to be found, amongst mosses, in 

 Dicranum tin elided inn and Hi/pnum h/tescens. In the Equi- 

 seta also the male prothallia are always smaller than the 

 females. 



Lastly, the reproductive cells of the Ttldzocarpece, Isoetes, 

 and Selaginella exhibit, according to their sex, the most 

 remarkable differences in their mode of development, size, 

 and form, so long as they continue in vital connexion 

 with the organism belonging to the generation following 

 impregnation. In the Coniferae the reproductive cells differ 

 in their origin and formation but little from those of phae- 

 nogams ; they differ only in the nature of the vegetative 

 growth subsequent to their formation which growth in 

 the Coniferae is in a high degree independent in the 

 formation of the row of cells in the interior of the pollen- 

 grain, as well as in the formation of the endosperm, and of 

 the corpuscula in the interior of the embryo-sac. 



There are so many essential points of agreement between 

 the Coniferae and the phaenogams, that it is more to the 

 point to get rid of the marked differences in their respective 



* The greater number of the Charseand Muscineae, a few only of the Equi- 

 seta, and all the known forms of Ferns and Ophioglossese. 



