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 IN ORCHIDE.^ AND ASCLEPIADE^. 519

undivided cavity, filled with minute granular matter mixed with an oily fluid ; and hence concluded that the fe- cundating matter was conveyed from the mass through the arm and gland to the stigma.

In the month of April last I saw, for the first time, di'awings of several Asclepiadcac made between 1S05 and 1813 by Mr. Bauer, who, aware of the interest I took in this subject, with his accustomed liberality and kindness, offered me any part of them for ])ublication.

Among these drawings, exceeding perhaps in beauty and in the completeness of the details all the other productions with which I am acquainted even of this incomparable artist, an extensive series, exhibiting the gradual develop- ment of the parts of the flower in Asdejnas anri-^savica, were the most important.

In this series, made in 1805, and commencing when the pollen is just separable in a pulpy mass from its cell, the glands of the undivided stigma being still invisible, the fact of the distinct origins of these parts is very satis- [7i9 factorily shown, in accordance with my observations in the essay referred to.^

But in these drawings Mr. Bauer has gone further than I did, having also represented the internal structure of the pollen mass as cellular; each cell in the flower-bud just before expansion being filled with a grain of pollen, marked with lines indicating its quaternary composition ; while in the ex])anded flower this grain is exhibited as shrivelled, having discharged its contents, which consist of a mixture of an oily fluid and minute granules. From this, the con- cluding stage of the scries, it may be inferred that j\Ir. Bauer's opinion respecting the mode of impregnation in Asclepiadeac agrees with that which I had adopted, and

' In a flower-bud imicli earlier Uian the commence. i-ent of Mr. Bauer's series I have found liic ))istilla lo consist merely of t;\{) distinct very short semicylindrical bodies, the rudiments no doubt of the futLU\3 stigma.

Ill this stage also the antherai are flat, nearly orbicular or ovate, greenish, rather thick and ojiaque, but petal-like, with no inequality of surface, or any other appearance of the future cells, which in a somewhat more advanced stage arc indicated by two less opaque areolae, and at the same time the two semi- cylindrical bodies unite to form the stigma. (Pi. 3G, figs. 7 — 11.)

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