6 



ON THE NATUEAL SYSTEM. 



Acanthacece as having the highly developed testa before referred to, will decidedly take their places as the highest developed forms of plants ; and the mass of the Perigynous and Hypogynous 

 families, according to their affinities, will then consequently find their places successively between the Epigynous Division and that Division in which these families are included. {V. Table VI.) 



The Divisions or Races of the Hypogynous and Perigynous Families. 

 In the attempt to execute this part of the arrangement many difficulties it is confessed had first to be surmounted. In the first place I have endeavoured to discover, by careful analysis, 

 of how many natural Divisions or Races the Perigynous and Hypogynous families can be regarded as consisting, and the comparatively great variety in their structure seems to make success 

 possible if not probable. 



The number of the Divisions being provisionally accredited, the next part of the analysis is to enquire, by the examination of every character showing affinity, how many of the Perigynous 

 and Hypogynous families can be referred, without doubt, to one or other of these Divisions. There then remains I believe very few of them which are at all osculant between the Divisions, and 

 these are arranged according to their more strongly marked affinities. 



It would be difficult however in words to fully describe the mode in which I have arranged the Perigynous and Hypogynous families, or at least the attempt would imply details which do 

 not seem at present called for, and I must refer to the Tables themselves for further explanation ; but the principle is so much the same as that which has led the authors of the Bryologia 

 Britannica to a natural arrangement of the genera of Mosses, {Introduction p. 6,) that the same words suffice as a limited explanation of it, substituting Division for " generic group," and families 

 for " species," which would make the passage referred to read thus : — " The natural arrangement combines into one Division all those families which have a stronger mutual resemblance of structure 

 in all parts, than to those of any other Division ; the sum of characters, and not any single character exclusively, being taken into account." I however believe that where genera occur having 

 what has been termed salient characters, and especially also exceptional characters, such as Donatia among Saxifragacece, they often show the position of a family more unequivocally than the 

 general characters, which may leave it more or less osculant. Thus the general character of Saxifragacece places them near Rosacece, but this genus and also others appear to me to show that 

 the resemblance, however close, is due to analogy only. In taking into account therefore " the sum of characters " such genera are frequently considered as the most certain guides to the position 

 of a family. That the mode of the arrangement of the Epigynous Division, Table II., is throughout natural I feel quite confident, and have for some length of time past ; and it also appears to 

 me as equally certain that the Perigynous and Hypogynous families must be subdivided on the same principles to arrive at the natural system of Exogens ; and in the Tables containing these families 

 it will be sufficiently obvious that the same principles are throughout adhered to, both in forming the Divisions and arranging the families contained in them. 



The Cryptogamous Families. 



The hypothesis that the apetalous families are apetalous forms of the polypetalous may I believe in an altered form be made applicable to the vascular Cryptogams relatively with the 

 apetalous, viz., by comparing them with the unisexual forms of the apetalous. Thus the inflorescence of each of the vascular Cryptogams consists almost exclusively either of the male or female 

 inflorescence of some one or more of the apetalous families, as far as regards external appearance, although in reality both sexes are usually included in it. But this perhaps will not be regarded 

 as an objection to such a comparison when it is recollected that ovaries frequently become anthers and occasionally bear anther lobes on their styles, and that anthers frequently bear ovules, while 

 the original form both of the carpel and anther is retained. In monstrous flowers of Cruciferce it is a common occurrence for disunited carpels to be antheriferous on one margin and to bear ovules 

 on the other, and in one instance an ovule was produced from the substance of an anther lobe, springing from its rima. 



Of these resemblances, the most prominent is that between Polypodiacem and Cycadece, the fronds of the former being analogous to the scales of the male flower of the latter. Lycopodiacea 

 would be probably the male inflorescence of Conifers and Gnetacea, as their female spore-cases do not differ in any external character from the male unless it is in size, and the latter appear identical 

 with those of Equisetacece, (Carruthers, Geol. Mag. Vol. II, No. xvi., Oct. 1865) -—Equisethcea would be the male inflorescence of Conifers, i.e., of such genera as Taxus, but as they show so 

 much the habit of Ephedra they may have more affinity with Gnetacem as the latter approach so nearly to Conifers ;— and MarsileacecB would be the female inflorescence of families in which 

 the placentation is dorsal, and I believe this comparison might be made even though the capsules of that family consist only of bracts. 



The approach between Polypodiacea and Cycadea is so close as to be well borne out by a minute comparison and makes it very probable that all the higher Cryptogams have a decided relation 

 to some apetalous family. The rings or rather compressed, flattened, oval masses of spore-cases of Marattia salicina and attenuata differ from the anther cells of Ceratozamia mexicana only in being 

 more numerous, (from six to ten or more instead of from three to five,) and in being adherent to each other laterally, for both the spore-cases and anther cells open internally, L e. towards the 



