On the Germination, Development, and Fructification of the Higher Cryptogamia, and on the Fructification of the Coniferae, Volumen65

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Ray Society, 1862 - 506 páginas
 

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Página 438 - The embryo-sac of the Coniferae may be looked upon as a spore remaining enclosed in its sporangium ; the prothallium which it forms does not come to the light.
Página 436 - Equisetaceas is very variable; its life is not of shorter duration than that of an individual shoot. It is a circumstance worthy of notice that in the second or .spore-forming generation of mosses and ferns, complicated thickenings of the cellwalls usually occur (witness the teeth of the peristome in mosses, the capsule-wall and the elaters in liverworts, and the vessels in ferns), whilst in the first generation these thickenings arc rare and exceptional.
Página 186 - Muscineae renders it probable that the large central cell is formed by the production of an excentrical, inclined, longitudinal septum in the young antheridium, followed by the production of another excentrical septum cutting the latter at right angles, and the subsequent formation of a longitudinal septum cutting both the above at an angle of 45°, such formation taking place after the apical cell of the antheridium has been isolated by a strongly inclined, almost horizontal septum cutting the primary...
Página 438 - ... converted into a sporangium, in the latter into an ovule. In the Conifers the embryosac also very early becomes detached from the cellular tissue surrounding it. The filling-up of the embryo-sac with the albumen may be compared with the origin of the prothallium in the Rhizocarpese and Sclagiuellio. The structure of the ' corpuscula' bears the most striking resemblance to that of the archegonia of Salvinia, still more to that of the Selaginellx.
Página 435 - In each case the body produced is exactly similar to the proembryo which originates from the germinating spore in both species. The vegetative life of the mosses is confined exclusively to the first, and the fructification to the second generation. The leafy stem alone sends forth roots : the spore-forming generation draws its nourishment from the first generation. The life of the fruit is usually much shorter than that of the leaf-bearing plant. In the vascular cryptogams this state of circumstances...
Página 435 - ... phaenogams. It is to be remembered that when new individuals are produced from single cells of the leaf of a moss, and also during the development of the gemmae of many mosses, the formation of the rudiment of the first leafy axis is preceded by the formation of a similar confervoid pro-embryo. This holds good as well in the mosses * as in those liverworts which possess a pro-embryo.
Página 171 - Translation, p. 171, note), says : — " I wish to add a few words as to the meaning "of the expression 'pro-embryo.' By the word 'embryo' is meant the bud capable " of developing leaves and roots. Thus, we speak of the embryo of the onion, the " potato, the hop. Now, when we 6nd in the vegetable kingdom organs which dif...
Página 186 - Vergleichenden Untersuchungen'' ') von der Entwickelung der Farrn-Antheridien giebt, weicht von den früheren nicht wesentlich ab. „The aiialogy to be derived from the process of development of the antheridia of the Muscineae renders it probable that the large central cell is formed by the production of an excentrical, inclined...
Página 432 - The period of the forties, just half a century ago, looks in the retrospect as one of almost dazzling discovery. To say nothing of the formal appearance of protoplasm on the scene, the foundations were being laid in all directions, of our modern botanical morphology. Yet its contemporaries...
Página 438 - ... of Pilularia, Salvinia, and Isoetes. The extinction of its sexual function (the protrusion of the pollen-tube) is preceded by a cell-formation in its interior, of which no instance is to be found amongst monocotyledons and dicotyledons. Two of the phenomena which have led me to compare the embryo-sac of the...

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