. The essentials of botany. Botany. 234 BOTANY. 435. The large spore likewise produces a very small sexual plant, which in this case, however, protrudes a little from the ruptured spore-wall. Upon this several archegones develop. After fertilization the germ-cell gives rise directly to a leafy plant, which emerges from the spore-wall in a way to re- mind one very forcibly of the growth of a plantlet from a seed. Fig. 140.âPlantletsof aLittle â, . ,, . Club-moss cseiagineiia mar- i his resemblance IS made greater tensli), showing cotyledons. I, two piantiets growing from one by the liKcness of
. The essentials of botany. Botany. 234 BOTANY. 435. The large spore likewise produces a very small sexual plant, which in this case, however, protrudes a little from the ruptured spore-wall. Upon this several archegones develop. After fertilization the germ-cell gives rise directly to a leafy plant, which emerges from the spore-wall in a way to re- mind one very forcibly of the growth of a plantlet from a seed. Fig. 140.âPlantletsof aLittle â, . ,, . Club-moss cseiagineiia mar- i his resemblance IS made greater tensli), showing cotyledons. I, two piantiets growing from one by the liKcness of the first leaves spore; p, tlie first stage (pro- â ' thallium). IT, a plantlet sepa- to COtyledonS (Fig. 140). rated from the spore; r, root;/, â¢' V & / Mlgnifl^d⢠'^ â * "*°°'"" But one genus, Selaginella (Family Selagmellacew) is known in tbis order. It contains 384 species, most of which are tropical. Two only (viz , S. rupestris and S. apus) are common throughout the United States, although six others are indigenous. Several exotic species are commonly cultivated in plant-houses. 436. The ftuillworts are all of one genus, Isoetes, of which there are seventeen species in the United States. Many botanists now hold that the Quillworts are more nearly related to the ferns {Filicinm) than to the Lycopods, and it is probable that this view may eventually be accepted. Fossil Lycopods.âTwo orders of Lycopods once existed, containing large trees, which appear to have been very abundant. The Lepido- dendrids (Order Lepidodendraceae) were a metre (3 to 4 feet) thick and 15 to 20 metres (45 to 60 feet) bigh, and seem to have had the general appearance of the Club-mosses. The Sigillarids (Order â¢Sigillariaceje) appear to have been trees 30 or more metres (100 feet) in height andl^ metres (4 to 5 feet) in diameter. Both produced two kinds of spores, showing their relationship to the Little Club-mosses and the Quillworts. Although very abundant in t
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Keywords: ., bookcentury1800, bookdecade1890, booksubjectbotany, bookyear1896
