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PHYTOGENESIS. 235 In still smaller cytoblasts it appears only as a sharply circumscribed spot; this is most frequently the case, as in the pollen of Richardia aethiopica, in the young embryo of Linum pallescens, and in almost all Orchideae (fig. 16); or, lastly, only a remarkable small dark point is observed. I have not, as yet, succeeded in discovering it in the very smallest and most transitory cytoblasts (in the leaves of Dicotyledons for instance). I have also found two in some very rare cases, but they occurred as exceptions to the general rule, and always where the majority exhibited the simple nucleus; for example, in Chamaedorea schiedeana (figs. 6, 7), Secale cereale, Pimelea drupacea (fig. 14); in the two latter I have sometimes found even three (fig. 15). The observations I have made upon all plants in which it was possible to trace the entire process of formation completely, lead to the conclusion, that these small bodies are formed earlier than the cytoblast (pl. I, figs. 1, 2); and I am almost inclined to conjecture that they are not altogether unallied to the nuclei which Fritsche has shown to exist in starch, and may probably indeed be identical with them. The size of this corpuscle also varies considerably, from the extent of half the diameter of the cytoblast to the most minute point, whose size could not be measured in consequence of the thread in the diaphragm of the microscope exceeding it so much in thickness. In the albumen of Abies excelsa I found it to average from 0·000045-0·000095 Paris inch; in Pimelea drupacea, from 0·00029-0·0003. Sometimes it appears darker, at others brighter, than the remaining mass of the cytoblasts. In general it has more consistency than the rest of the cytoblast, and continues sharply defined after that has been changed by pressure into an amorphous mass, as in Pimelea drupacea for example.

There is a second point, on which I must say a few words, in order to be enabled to express myself more briefly hereafter without being unintelligible, which relates to the different inorganic substances that occur during the vital process of plants, and pertain to the series of starch and woody fibre. I make no pretensions whatever to a complete enumeration of all