;-i VASCULAR CRYPTOGAMS. 



leaf-Stalk even before the first appearance of its lamina, and before the differentiation 

 of its tissue. A single superficial cell of the leaf-stalk is the mother-cell of the new 

 shoot ; and as the surrounding tissue of the leaf-stalk grows like a wall around them, 

 they may, as in Pteris, be placed in a deep depression, where they sometimes remain 

 dormant for a long period. Even when the leaf has long died away, the leaf-stalk 

 still remains succulent above the bud, and filled with food-materials ; and in 

 Aspidium Filix-mas vigorous stems are not unfrequently found with a number of 

 leaves at their posterior end still attached to the leaf-stalk of an older stem. In 

 some cases, as in Struthiopteris germanica, the buds produced on the leaf-stalks 

 develope into long underground stolons furnished with scale-leaves, which become 

 erect at the end and unfold a crown of foliage-leaves above ground. In Nephro- 

 lepis undulata they swell at the end into tubers. Adventitious buds spring from the 

 lamina, especially in many species of Asplenium ; in A./urcaium, e. g., often in large 

 numbers from the middle of the upper surface of the pinnae; in A. deciissatiim from 

 the base of the pinnse (or axillary on the mid-rib ?). Ceratopteris thaliciroides not unfre- 

 quently produces buds in the axils of all the divisions of the leaves, which, especially 

 when the detached leaf is laid upon damp ground, germinate rapidly, and grow into 

 vigorous plants. According to Hofmeister, these buds also spring from superficial 

 cells of the leaf. The long pendulous leaves of some Ferns touch the ground with 

 their apices, root, and sometimes also put out new shoots from these points {e.g. 

 Chry sodium flagelli/erum, Woodwardia radicans, &c.). 



The Roofs. During its growth the stem is usually constantly forming new roots 

 in acropetal succession, which, in the creeping species, become at once fixed to the 

 substratum. In Pteris aquilina the new roots appear close behind the apex, and, both 

 in this species and in Aspidium Filix-mas, they also proceed from the adventi- 

 tious buds of the leaf-stalk while still very young. It has already been mentioned 

 that, in the last-named species, when the mature stem is completely covered by 

 leaf-stalks, all the roots spring from them and not from the stem. In Tree-ferns 

 especially the lower part of the erect stem is entirely covered by slender roots, 

 which grow downwards, forming an envelope several inches thick before they 

 penetrate the soil, and thus give a broad base to the stem although it is there 

 really much more slender ; but in the upper part there are also a great many roots. 

 In small plants they are very slender ; on large plants they attain a diameter of 

 from I to 3 mm. ; they are cylindrical, generally covered with a number of root-hairs 

 which form a kind of felt, and are of a brown or black colour. The history of 

 the growth of Fern-roots has been studied by Nageh and Leitgeb^ The apical 

 cell is a three-sided pyramid, with a convex equilateral base. The segments or 

 layers of the root-cap detached by convex septa parallel to the base first separate 

 into four cells placed crosswise, so that those of successive layers alternate by 

 about 45° ; each of the four cells of a layer then splits up into two external and 

 one internal (central one), so that the layer is now formed of four internal cells 

 arranged in a cross, and of eight external cells. Further divisions may then follow ; 



* Sitzungsber. der bayr. Akad. der Wiss. Dec. 15, 1865. Compare with what follows the 

 diagram of a root given under the Equisetaceoe, which serves in the main also for Ferns and 

 Rhizocarps ; also in addition p. 123. 



