TYPES OF VARIATION 55 



base of the frond, and even in some instances converting these into 

 lateral fronds, the whole representing a trident when they grow 

 upwards at an acute angle to the main rachis or midrib. Congested 

 and imbricate forms occur in several species. In these the midribs, 

 main and secondary, are shortened so that the divisions of the 

 frond are compressed, and sometimes densely overlap, the result 

 being a great reduction in size, forming a dwarf section of very 

 pretty Ferns. The above varietal sections are, as we have seen, 

 mostly of a redundant type, exceeding the normal in development, 

 or, at any rate, no part of the normal plan is missing, but there are 

 others which vary in the opposite direction, and although these, 

 as a rule, belong rather to the " curio " class than to the elite, 

 this is not always the case, as will be seen in A. f. f. Victories (Ap- 

 pendix No. XIII), which is imputed to the non-redundant, because 

 it is assumed that the twin pinnae represent only the enlarged basal 

 pinnules of the pinnae proper, the rest of which is lacking. Whether 

 this theory be correct or not is immaterial ; in any case this 

 wonderful Fern is a development of the phenomena of " cruciation," 

 a small varietal section similarly characterized by twin pinnae set 

 on at an angle to each other, and thus, with the opposite pairs, form- 

 ing crosses, whence the name of " cruciate." 



As a section of truly non-redundants, we may mention the trun- 

 cate and the medio deficiens forms. In the truncate we have, as it 

 were, the converse type to the cristate, since, instead of the midrib 

 multiplying itself, it suddenly leaves off before its work is finished, 

 terminating with a projection like a thorn at the squared-off end 

 of the frond and side-divisions. In Lastrea montana this is found 

 so frequently as to be termed "the beginner's Fern" by Fern- 

 hunters. This occurs also in the Lady Fern {A. f.f. excurrens), 

 Male Fern, and in various forms in the Hartstongue (5. v. pera- 

 jcrens, cornuium, etc.) Why, in thoroughly healthy, robust plants, 

 the growth should thus suddenly cease is a puzzle, and it is curious 

 that in the Tulip Tree {Liriodendron tulipifera) the leaves should 

 be square-ended on similar lines. In the medio-deficiens type, the 

 subdivisions of the pinnae, and sometimes of the pinnules, are 

 aborted or reduced to rudiments next the midrib, leaving an open 

 space, which in one form of Lady Fern found in Wigtonshire by the 

 writer is so even as to render the frond pretty, and in the lineare 

 section of Shield Ferns it imparts a graceful habit. 



Another distinct type is that in which the fronds and side 

 divisions are convexly curved " revolvens " or erratically twisted 

 " flexuose," examples of which have been found in the Lady Fern, 

 the Male Fern, the Hartstongue, the Hard Fern, the Soft Shield 

 Fern, and the Common Bracken. A peculiarity of both these types 

 is that the curving tends to contravene one of the laws of plant life, 

 viz., that of the self-exposure of leaf surfaces to best advantage as 

 regards light. The curving, rolling, or twisting tends to expose the 



