MATURE SPOROPHYTE 15 



of the nineteenth century were indeed the heroic age of Plant Morphology, 

 and the results then attained will always continue to be the basis of com- 

 parison, as applied to the ascending series of green plants. It must, 

 however, be remarked that those results were achieved on a purely comparative 

 footing, and at the moment carried no further interpretation with them. 

 For these were the days before evolutionary theory held sway in the 

 Biological sciences, and accordingly no underlying phylogenetic meaning 

 was as yet seen in the facts observed and compared. But eight years 

 later Darwin's Origin of Species was published, and " the Theory of Descent 

 had only to accept what genetic morphology had actually brought into 

 view." It is also to be noted that at first no past physiological history 

 was traced in the facts of the individual life ; this line of interpretation suffered 

 much longer delay, and is even now only gradually becoming apparent. 

 As we shall see, however, such a meaning and such a history may still 

 be found reflected in those successive phases of the individual life which 

 Hofmeister and his predecessors were able to detect and to compare. 

 It is along lines such as these that we may best seek for the solution of 

 the problem presented by the origin of a Land-Flora. 



It will then be essential for our purpose, in the first place, to follow 

 through all its phases the life-history of certain typical organisms, and 

 we shall best begin with those which occupy a middle position in our 

 system, viz. the Pteridophytes. The common Male Shield Fern (Nephrodium 

 Filix-mas. Rich.) will serve as a familiar, and also a suitable example. 



This Fern is known to every one as growing in woods and hedgerows, 

 and even in more exposed situations, such as the open gills and hill-sides 

 of higher-lying districts. It presents a robust appearance, and when fully 

 developed it consists of an oblique and massive stock, which is relatively 

 short : this is entirely covered over by the bases of the leaves, of which 

 the youngest constitute a closely packed terminal bud (Fig. i). Those 

 leaves which are situated further from the apex, and immediately below 

 the terminal bud, may in summer be found to be of large size and 

 compound structure (Fig. 2) ; they are of a rather firm texture : individually 

 they are in outline not unlike the ancient Greek shield, and collectively 

 they form a crown-like series surrounding the terminal bud. Passing again 

 further back from the aprex of the stock, its surface is found to be closely 

 invested by the bases of the numerous leaves of former seasons, the 

 upper portions of which, having performed their functions, have rotted 

 away. If the plant be dug up, and the soil carefully removed from it, 

 an ample root-system will be seen, consisting of thin, wiry, and dark- 

 looking fibrils, which spring from the basal parts of the leaves, and may 

 bear numerous branch-rootlets. 



All these parts consist of tracts of tissue differentiated to subserve 

 distinct functions. The Vascular Skeleton, which appears as a cylindrical 

 network of strands within the massive axis (Fig. i, E, F), throws off 

 continuous and connected branches, on the one hand into the leaves, 



