Bulletin of the Torrey Botanical Club/Volume 8/Onoclea sensibilis L. var. obtusilobata
§ 95. Onoclea sensibilis, L., var., obtusilobata, Torr.——Spending a portion of my summer vacation in Litchfield Co., Connecticut. I have made some observations among the ferns of this section which are found in abundance and profusion rarely equalled.
Camptosorus grows to some extent on the granitic rocks of this vicinity. I have never found it before except on highly calcareous rocks.
Ophioglossum vulgatum, L., is found in bogs, the sterile segment fully 3½ inches long.
"Frondosa forms" of Osmunda cinnamomea, L., occur, some with the fronds half sterile, half fertile, while Osmunda regalis, L., occasionally has the frond fertile in the middle!
The most interesting forms, however, were the variations of Onoclea sensibilis, L., which would have furnished ample constructive material for some of our more ardent variety manufacturers. In a low, rocky meadow near West Goshen the following graded series was found:
A. Normal fertile fronds with secondary rachises erect and appressed to the primary.
B. Fertile fronds. Segments all normally bead-like; secondary rachises spreading, regularly inclined to the primary about 35°.
C. Fertile fronds. Fully bipinnate; lower segments bead-like, the upper partially unrolled; secondary rachises spreading.
D. Var. obtusilobata, Torr. Pinnae pinnatifid throughout their whole extent; segments very strongly revolute, those nearest the base of the pinnae sometimes bead-like, as in normal fertile fronds; sporangia present in some of the indusia, even when the segments are only moderately revolute.
E. Sterile fronds. ½–⅓ the normal size; pinnae cut entirely to the midribs in their lower half; primary rachis wingless; margins moderately revolute; indusia present, conspicuous, 2-6 to each segment; sporangia none, or merely rudimentary.
F. Sterile fronds. Form similar to "E" but with pinnae less deeply cut and with mere traces of indusia on the basal segments.
G. Sterile fronds. Size and outline normal; primary rachis only slightly winged; margins slightly revolute.
H. Normal sterile fronds with primary rachis broadly winged, except between the lowest pairs of pinnae.
It will thus be seen that there may occur all possible forms intermediate between the sterile and fertile fronds, and that Dr. Torrey's var. obtusilobata is on the boundary line between the two.
In the present instance the cause of this variation seemed very apparent. The meadow in which these forms were found was cut late in June, before the fertile fronds were grown, thus destroying the earlier-formed sterile fronds. The vitality of the plant thus finding no outlet save through the growing fertile fronds, and the plant requiring an expanse of foliage, a result was reached intermediate between the fertile and sterile fronds. The following facts may serve to substantiate this view:
1. Wherever the sterile fronds had been entirely cut away, the variations appeared which approximated most closely to the sterile fronds.
2. Where the sterile fronds were only partly destroyed on one rhizoma, variations appeared not very divergent from the normal fertile fronds.
3. Where the sterile fronds remained intact, no variations were found, even after diligent search.
4. In places where the plants were too much reduced to bear fertile fronds under favorable conditions, no variations occurred, even when the sterile fronds were entirely cut away.
Whether the above explanation will prove satisfactory for all forms of the so-called var. obtusilobata wherever found, remains an open question; as a true variety, however, obtusilobata has no place, and it would be well if many more of other numerous forms that have been raised to the dignity of varieties could be consigned to a grave so secure.
|West Goshen, Conn.||Lucien M. Underwood|