Seedless Vascular Plants

摘要: Prior to research with the electron microscope, little detailed information was available on ontogeny and structure of sieve elements in seedless vascular plants. About all that could be said about mature sieve-element protoplasts this diverse group plants they generally had a very clear appearance, contained variable numbers structures called refractive spherules, apparently lacked nuclei. Little known connections or sieve-area pores between contiguous because their are too small (0.5 μm less diameter most plants) satisfactorily examined light microscope.