THE PLANT WORLD 3 



It is interesting to note that in both of these species the lower part of 

 the frond is usually most like the true fertile condition. 



The sterile frond of the narrow-leaved chain fern ( Woodwardia 

 angiistifolia or W. areolata) is mistaken by beginners for that of the 

 sensitive fern. The fertile frond is taller, has a dark brown stem, and 

 its pinnae are long and narrow and are not connected (except near the 

 tip) by a broad green wing, but only by slight ridges on the rachis. 

 Where the fern is at all plentiful it is easy to find all sorts of interme- 

 diate forms, three of which are shown in the illustration (l, 2, 3). As 

 they depart from the fertile type, the pinnae change from linear to 

 lanceolate, bear fewer fruit-dots and are thinner in texture, while the 

 ridges become wing-like. This is shown in the case of the two larger 

 fronds in the illustration. The transition is not always symmetrical. 

 On one side of the frond at the left the pinnae are like the usual fertile 

 ones, those on the opposite side being sterile except the upper three or 

 four that bear some fruit-dots. A bit of a normal fertile pinna is shown 

 at 4. The middle frond (2) represents a peculiar sterile form that is 

 found in all sizes, some of them being as tall as the fertile ones. Now and 

 then the lower pinnae bear a few fruit-dots. Some of these have yellowish- 

 green stems, but others show by their dark stems and contracted pinnae 

 an approach to the fertile fronds. There is no evidence that these forms 

 were produced by any injury to the plants. 



In the Osmundas — that is, the royal, the interrupted, and the cinna- 

 mon ferns — the fertile portion is reduced to the stalks and the midribs 

 and veins upon which the nearly sessile sporangia are borne. A form of 

 the cinnamon fern (O. cmnamomea froiidosa) with partially contracted 

 fertile fronds has long been known. A bit of a pinna is shown at 6, 

 while at 7 is a tip of a normal fertile pinna. It will be seen that the 

 spore-cases are scattered along the edges or near them, and are not clus- 

 tered in fruit-dots of any definite shape. Here again this condition seems 

 to be brought about by an injury to the plant early in the season of 

 growth. The first fronds of the plant from which our specimen was taken 

 were destroyed by fire early in the season. 



A curious form of the interrupted fern (O. Claytoniana) which has 

 been named diibia seems • to resemble this form of the cinnamon 

 fern. We have never seen specimens, but the " sterile and fertile inter- 

 graded, as some of the pinnae were wholly fertile and others bore both 

 fertile and sterile pinnules. Some of the pinnules even were in shape 

 and texture like the sterile pinnules but had sporangia at their edges." 

 According to the discoverer, A. J. Grout, this form does not seem to be 

 due to "mutilation or peculiarities of nutrition." The cutting of the 

 sterile fronds is also somewhat different from the normal. 



In a swamp where there is keen competition for existence, I saw last 



