THEIR CYTOLOGICAL DISTINCTION 61 
Nephrodium Filix Mas, as occurring on the leaf-bases (Fig. 1), and in 
Cystopieris bulbifera, at points on the upper region of the leaf (Fig. 3). 
It also occurs in various forms in many other Ferns, in Lycopods, and 
Equiseta. The essential feature of it is that a portion of tissue of the 
sporophyte, developed as a bud with axis leaves and roots, on being 
detached from the parent plant, may continue its growth apart from the 
parent. This is plainly a mere vegetative amplification of the sporophyte 
itself, and its tissues are at first continuous into those of the bud: there 
is no reason to think that any nuclear change accompanies the production 
of these growths, and the result is the establishment of physiologically 
independent individuals; but their origin and detachment do not modify 
our conception of the sporophyte as a whole in any essential point. If 
that conception be based upon nuclear changes accompanying fertilisation 
and reduction, it will include all such results of vegetative amplification : 
they will be held to be intra-sporophytic means of propagation. 
Similarly, in the case of gametophytic budding, which is common in 
Liverworts, Mosses, and in certain Ferns, by means of gemmae: these 
are small bodies, consisting of one or more cells, which are easily 
detached and under suitable conditions develop into new gametophytes. 
Here again the gemmae appear to be mere vegetative growths, and 
they secure increase in number of physiologically independent individuals ; 
but there is no reason to think that there is any nuclear disturbance 
involved: they may be regarded as intra-gametophytic means of propagation. 
How, then, do the irregularities above described affect the general view 
of the cytological distinction between the two alternating generations of the 
Archegoniatae? It is quite clear that an absolute chromosome-distinction 
cannot be held as universally applicable at the present time to the two 
alternating phases: nor does form depend on the exact number of the 
chromosomes: nor yet is there any obligatory ratio according to which 
the gametophyte is always haploid and the sporophyte always diploid. 
These facts give an opening to the facile conclusion that the chromosome- 
distinction is worthless, and opinions to this effect have already been 
expressed. But the recognition of the present existence of aberrant forms 
does not negative the importance of the relation which is usually seen, 
nor exclude it from taking its due place in the reconstruction of the 
history of the past. It is contrary to all evolutionary theory and 
experience to assume that what has been normal in the past is 
obligatory for the present or the future. Moreover, it seems probable 
that these abnormalities do not represent anything which took a settled 
place in the course of the evolution of the plants in: which they appear: 
our opinion might be different if in any of the great phyla it could be 
shown that a definite stock, or line of descent, had been permanently 
established showing aberrant characters; for instance a permanent Arche- 
goniate phylum showing a cycle without any chromosome-differences. But 
of this there is no evidence at all: every one of the main phyla 
