ON THE HIGHER CRYPTOGAMOUS PLANTS. 119 



existence of a distinction of sexes in these families. In the second place, we 

 have to endeavour to trace the analogies which exist between the different 

 conditions presented by the supposed sexual organs in the different families. 

 These considerations, if we adopt the hypothesis of sexuality, lead to some very 

 interesting questions in reference to the process of reproduction generally. 



In regard to the first question, that of the existence of two sexes and the 

 necessity of a process of fertihzation, we have several kinds of evidence. 



1. The inferences to be deduced from the universality of the existence of 

 two kinds of organs in connexion with the reproductive process. We have 

 seen that these exist in all the families at some period or other of the life of 

 the representative of the species. In the Mosses and the Hepaticae they occur 

 in the fully developed plant. In the Ferns and Equisetacese they occur upon 

 cellular structures of frondose character developed from all the spores, which 

 frondose bodies or pro-embryos have an existence of some permanence, espe- 

 cially in the Equisetaceae. In the Lycopodiaceae, the Isoetaceae and Rhizo- 

 carpese, the pistillidia occur upon very transitory cellular structures produced 

 from one kind of spore, the larger, while the smaller spores at once develope 

 in their interior cellules containing moving spiral filaments such as occur in 

 the antheridia of the other families. 



2. The inferences to be deduced from the observations on the development 

 of those plants in which the two kinds of organs, occurring in distinct places, 

 can be separated. Strong evidence has been brought forward that the dioecious 

 Mosses, as they are called, do not produce sporangia when the pistillidia are 

 kept apart from the antheridia by natural accident. The majority of observers 

 state that the large spores of the Rhizocarpeae do not germinate if the small 

 spores are all removed from contact with them ; a few counter-statements 

 however do exist. Again, the majority of authors, and all the recent ones, 

 state that only the large spores of the Lycopodiaceae and Isoetaceae produce 

 new plants ; while some older writers believed that they had seen the small 

 spores do so. 



3. The direct observation of a process of fertilization, of which we have 

 only testimony from two authors, Suminski and Mercklin, in reference to 

 the Ferns alone ; since the assertions of Schleiden in regard to the Rhizo- 

 carpeae have been demonstrated by Nageli, Hofmeister, and Mettenius to 

 have been based on very imperfect observation. 



The circumstantial evidence furnished under the first head seems to rae 

 very strong, so much so that I am inclined to adopt the idea of sexuality on 

 this ground as the legitimate provisional hypothesis arising out of our present 

 knowledge, especially when supported so strongly as it is by the negative 

 evidence indicated under the second head. 



The positive evidence of the third head is certainly very insufficient as 

 yet, considering the extreme delicacy of the investigation. Suminski's other 

 observations on the details have been contested in many particulars ; and 

 Mercklin, the only other observer who asserts that he has seen the spiral 

 filaments within the so-called ovules, describes the conditions differently, and 

 states that he has only been able to observe them positively there three times. 

 At the same time the difficulty of the investigation should make us hesitate 

 in attaching too much weight to the failure of the other observers in tracing 

 a process of fertilization ; moreover it is quite possible that actual entry of 

 the spiral filaments into the canal of the ovules or pistillidia is not always, if 

 ever, necessary. 



The facts before us, then, appear to me strong enough to warrant the 

 adoption of the views propounded by the latest authors on this subject, and 



