OF ARTS AND SCIENCES. 183 



oblanceolate blade, which is about 6 mm. wide. The terminal portion 

 of the blade has disappeared through erosion, but at the tip on either 

 side are seen two narrow strips (cf. Fig. 3, E) of the membrane of 

 the original blade still jiresent. The rest of tlie blade is more com- 

 plex in its structure. The cryptostomata are much more numerous 

 and much more conspicuous. They are much larger towards tlie tip 

 of the blade, and become smaller and smaller as they approach the 

 base, until at the place where the blade passes over into the stipe 

 they disappear altogether. Hence it is reasonable to assume that this 

 transition place, as we may call it, the " Uebergangstelle " of German 

 writers, is a region of active growth. 



Third Period. — 1. Development of the Rhizogen. — Very soon after 

 the primitive or simple membranaceous blade has thus been very nearly 

 replaced by a blade of more complex structure, and the stipe has 

 elongated to a somewhat greater extent, we come to the beginning of 

 a set of changes in the lower portion of the stipe, which are of great 

 importance in establishing the relationships between this species and 

 others of the same group. The holdfast or organ of attachment iu 

 this stage differs from that of the preceding merely in its somewhat 

 greater size. In some of the specimens, however, the holdfast is a 

 vertically elongated body of narrowly conical shape. This variation 

 seems to be the result of peculiar conditions in the substratum to which 

 the plant is attached. The stipe iu the specimen chosen as a good 

 illustration of this stage (cf. Fig. 4) is about 8 mm. long and 0.5 mm. in 

 diameter. It is for the greater part of its length cylindrical, but at 

 about 2 mm. from the holdfast it appears somewhat swollen (cf. Fig. 

 4, B). This swelling, which is regularly ellipsoidal in general outline, 

 is in the specimen chosen about 2 mm. in height and 1 mm. in diam- 

 eter. Even before this swelling becomes evident, that portion of the 

 stipe where it is to appear seems denser, and is therefore of a slightly 

 different color from the neighboring portions, although at the time it 

 is hard to detect that the surface is at all curved outward. The swell- 

 ing or node is very readily seen, both in fresh and in alcoholic 

 specimens, and is very nearly as distinct in specimens pressed for 

 preservation in the herbarium. 



This swelling is described by De la Pylaie in the " Flore de Terre 

 Neuve " (pp. 49 and 50), and was observed by him in plants thrown 

 ashore about the end of October. His description of a young plant 

 is so excellent that I reproduce it here. " Tout le vegetal n'avait 

 alors que 2 a 3 centimetres de hauteur, et sa fronde, d'une delicatesse 

 infinie, n'avait en largeur que 3 millimetres au plus. Cette fronde ua 



