THE HIGHER CRYPTOGAM IA. 439 



Isoetes. The extinction of its sexual function (the protru- 

 sion of the pollen-tube) is preceded by a cell-formation in 

 its interior, of which no instance is to be found amongst 

 monocotyledons and dicotyledons. 



Two of the phenomena which have led me to compare 

 the embryo-sac of the Coniferae with the large spores of the 

 higher cryptogams, is common to the embryo-sac of phaeno- 

 gams, viz., the origin of the ovule from an axile cell, and 

 the want of connexion with the adjoining cellular tissue. 

 This is very remarkable in the Rhinanthaceae on account of 

 the independent growth of the embryo-sac. The Coniferae 

 are closely allied to the phaenogams in the fact that their 

 pollen-grains develope tubes. 



The phasnogams therefore form the upper terminal link 

 of a series, the members of which are the Coniferae and 

 Cycadeae, the vascular cryptogams, the Muscineae, and the 

 Characeae. These members exhibit a continually more 

 extensive and more independent vegetative existence in 

 proportion to the gradually descending rank of the gene- 

 ration preceding impregnation, which generation is deve- 

 loped from reproductive cells cast off from the organism 

 itself. The closing members of this series, the Characeae, 

 pass through their entire vegetative development in this 

 generation, whilst the vital phenomena of the generation 

 which follows impregnation are limited to the filling with 

 oil and starch of the newly formed cell in the central cell 

 of the fruit-branch or archegonium. The development of 

 the latter generation in the Muscineae is far more important, 

 although in some instances, as for example in Riccia, it is 

 very limited in comparison with the first generation, that 

 namely which precedes impregnation.* This state of things 

 is reversed in the Ferns, the Equiseta, and the Ophioglosseae. 

 From the Characeae up to these orders, there is an uncer- 



* Anthoceros — which in the development of the second generation stands 

 very low in the scale — exhibits a remarkable analogy with the Characege, in the 

 fact that, as in the latter, the formation of its antheridia commences by the 

 growing out of the cells of the wall of an intercellular cavity. The well-known 

 red globules of Chara are manifestly states of antheridia. Cavities com- 

 municating with one another are formed round the middle point of the hitherto 

 solid globular mass of cells, within which cavities the antheridia — or cellular 

 threads in whose joints the vesicles which produce the spermatozoa are formed 

 — become developed. 



