274 PHILOSOPHICAL NOTES ON 



might be ascertained what percentage of seedlings vary from the 

 parental type. 



Botanists, in cases where there are more embryos than one, call 

 them adventitious, that is, according to so-called rule, they have 

 no business to be there, they are accidental ; but this word 

 explains nothing, and, moreover, as in the Citrus, this adventitious- 

 ness is so frequent, we must look upon it as rather the rule than 

 the exception. To the believer in the theory of evolution and 

 descent, there must be some more logical way of accounting for 

 them. 



Now, by referring them back to a class of plants which is low 

 in the scale of development, we may, perhaps, find a hint of what 

 this polyembry really means. The sorus of ferns is a placenta, 

 from which emerge numerous sporangia, each containing numerous 

 spores or embryos. A partial reversion of the Citrus seed to this 

 ancestral mode of seeding may, perhaps, not be an illogical way 

 of accounting for these adventitious embryos. We call it rever- 

 sion, but for all we know it may be a continuation of an ancestral 

 mode, without interruption. 



Under the heading of oil-glands I referred the origin of the 

 dots on the Citrus leaf to the conceptacles of certain seaweeds. 

 Seaweeds might not inappropriately be called water-ferns. Not 

 impossibly, both in its oil-glands and in its polyembry, the Citrus 

 may repeat remnants of characters which were of importance in 

 its very distant progenitors. 



Evolution demands some homology between the spore and the 

 embryo of the ovule. In the Citrus seed as many as 40 embryos 

 have been observed in one seed, so that it would appear this seed 

 is often a nest of buds, emerging from a common placenta. This 

 polyembry might be explained by a contraction of a bunch or 

 raceme of embryos, included in one seed. 



In the Citrus seed, at all events, the homology between ovule 

 with many embryos and the sorus of ferns appear to me clear. 

 The embryos of the seed being homologous with individual 

 spores. 



Systematic botany has so long impressed upon us that ferns are 

 different beings from flowering plants that we cannot now readily 

 divorce our minds from the idea that they are totally <listinct. 

 But in what does the rhizome of a fern diiFer from the rhizome 

 of any flowering plants ? 



