. The fern allies of North America north of Mexico. Pteridophyta; Botany. THE AQUATIC QUILLWORTS. feet below the surface, a colony of plants like small green rosettes, he may conclude that he has found Braun's quillwort (Isoetes echinospora Braunii). Since all the aquatic quillworts have the same general plan for the plant body, it is possible that such a conclusion may have to be modified later and his specimens referred to some other species, but Braun's quillwort is so abundant and so widely distributed that until its spores have been ex- amined one is fairly safe in assuming that any new f
. The fern allies of North America north of Mexico. Pteridophyta; Botany. THE AQUATIC QUILLWORTS. feet below the surface, a colony of plants like small green rosettes, he may conclude that he has found Braun's quillwort (Isoetes echinospora Braunii). Since all the aquatic quillworts have the same general plan for the plant body, it is possible that such a conclusion may have to be modified later and his specimens referred to some other species, but Braun's quillwort is so abundant and so widely distributed that until its spores have been ex- amined one is fairly safe in assuming that any new find is this species. The leaves are from ten to thirty in number and occa- sionally reach a length of ten inches, though the average is probably less than five. They are dark green, occasion- ally reddish at base, and while in the water are half erect. When fresh from the water they are somewhat rigid and inclined to curve backward. There are a few stomata present on the tips of the leaves, but the peripheral bast bundles are absent, as is usual in the submerged species. The sporangium is pale spotted, and the velum or in- dusium about half covers it. The principal distinguishing charac- ter is found in the megaspores. These are from 35O1" to 550," in diameter and covered with broad spinules which are often forked or toothed and sometimes recurved. Occasionally, too, the spin- ules may become confluent into short crests. The microspores are from 26/* to 30/* in length, white or grey in colour, smooth, and very numerous. Three hundred thousand microspores have been found in a single sporangium. The spores retain their vitality for some time, and plants have been raised from the spores taken from herbarium Megaspore of Isoetes echinospora Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original
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Keywords: ., bookcentury1900, bookdecade1900, booksubjectbotany, bookyear1905
