TN 0RCH1DE.E AND ASCLEIMADE/E. 533
tubes have fiiiislicd their growth, would afford an ari^ni- nient of souie weight at least agaiust their esseutial iinj)or- tance in any case ; and it may be added, that in Ascle- piadeae there appears to be no other source of nourishment for the tube until it has penetrated into the style, than these granules. Nor is it necessary to suppose that the tubes tliemselves act directly, it being even probable that they also contain a fluid or granular matter much more minute than that originally filling the cavity of the grain. ^ Our knowledge indeed appears to me not yet sufficient to warrant even conjectures as to the form of the imme- diate agent derived from the male organ, or the manner of its application to the ovulum in the production of that series of changes constituting fecundation. I may, how- ever, be allowed to observe, that at present, with respect to this function, we are at least as far advanced in these two families, hitherto considered so obscure, as we are in any other tribe of Phaenogamous plants : and I even venture to add, that in investigating the obscure subject of generation, additional light is perhaps more likely to be derived from a further mhmte and patient examination of the structure and action of the sexual organs in Asclepia- dca3 and Orchideae, than from that of any other department cither of the vegetable or animal kingdom.
' See Additional Observations.
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