60 
REPORT ON BOTANY, MDCCCXLI : 
Treviranus lias likewise observed, that a cavity is situated be- 
neath these hairs, which penetrates into the style, without, 
however, communicating with the conducting cellular tissue. 
The Style Hairs of Campanula medium have been repre- 
sented in the Icon. Anat. Bot. tab. 21, fig. 1 and 4. It can 
be seen, that a channel enters from the hair into the style, 
without, however, being connected with the duct of the style. 
The drawing back of the hair I did not find ; but it appears to 
me, as if the fore-part of the hair lost itself in and sunk into 
the lower. There were tubes similar to pollen tubes in the 
style, but forced together, and before the opening of the 
anthers (fig. 1). The duct of the style is closed below both 
before and after the opening of the anthers, but open above 
(figs. 2, 3). Pollen tubes were seen in the duct after the open- 
ing of the anthers, and differ from the lengthened papillsB with 
which I placed them in the explanation of the figures ; they 
are also thus delineated, as the few papillse strewed about in 
the duct may have got into it by the incision. It is singular, 
that pollen tubes should have been found in the duct of the 
style before the bursting of the anthers ; but this requires 
further investigation. 
Pollen tubes, in the state in which they penetrate the 
ovule, are illustrated in the Icon. Anat. Bot. part ii. (1840), 
tab. 8. The micropyie of the ovule of Mesemhryanthemum 
glomeratum is much larger than the entering pollen tube 
(fig. 2), and no trace could be perceived of an opposing em- 
bryo sac, or of any other change taking place within. The 
same was also the case upon the penetrating of a pollen tube 
into the ovule of the Hohenbergia bilbergioides (fig. 3) ; each 
ovule in the ovary was provided with such a pollen tube. The 
pollen tubes of the same plant, as they are produced from the 
pollen grain, are represented, fig. 4, in which the perfect cor- 
respondence between the tube, which forces its way into the 
ovule, and the sac which has just been developed, may be ob- 
served. Fig. 5 exhibits two ovules of Gymnadenia conopsea, 
into which pollen tubes are entering. The integument of the 
ovule is so tender and transparent, that the absorption of the 
sac, as soon as it has entered, may be distinctly observed. The 
458 
