1885.] 



MICKOSCOPICAL JOURNAL. 



75 



fovilla, are discharged and taken up 

 bv the conducting tissue of the style. 

 If the st\'le be torn open and the 

 fibrillar of the conducting tissue sepa- 

 rated, the fovilhi in it is easily trace- 

 able all along in streaks and blotches 

 down to the ovarv. Here the conduct- 

 ing tissue spreads itself out over the 

 walls of the ovarv and the placenta, 

 accompanies the funiculi to their junc- 

 ture with the ovules. The tuft of 

 papilliE surrounding the micropyle of 

 the ovule, which on bending round on 

 its long funiculus is brought in easy 

 contact with the minute papilUi? which 

 beset its ventral portion, the fertiliz- 

 ing element is absorbed ; thus also 

 communicated to the oosphere in the 

 embryo sac and the process of fertili- 

 zation is accomplished. 



According to Mr. Britton the num- 

 ber of pollen-tubes depends on the 

 number of ovules, and he says the 

 former are generallv in excess of the 

 latter. The ovary of Cereus grandi- 

 Jlora contains at least 3,000 ovules ; 

 the stvle is a tube about 8 inches long 

 and has a very small channel ; the 

 fibrillin of the conducting tissue, which 

 are also tubular, till up the body of 

 the style ; more than 3,000 pollen- 

 tubes must therefore seek their way 

 down to the ovarv. Such a mass of 

 foreign material in the style should 

 certainly leave a trace behind ; but 

 I have never discovered any. Trans- 

 verse sections of the style before and 

 after pollinization are similar in ap- 

 pearance, but the style on being laid 

 open longitudinally after polleniza- 

 tion contains plenty of fovilla granules 

 throughout the conducting tissue. 



Mr. Detmer, in a paper also cited 

 by Mr. Britton, has undertaken to 

 trace the course of the pollen-tubes 

 in angiosperms ; I have corresponded 

 with him and also with Mr. Stras- 

 burger on this subject, pointing out 

 to them the impossibility of pollen- 

 tubes reaching the micropyle of the 

 ovules in certain plants in the way 

 indicated. I submitted them also 

 some of my preparations ; but our cor- 

 respondence remained without I'esult, 



the gentleman named first having not 

 the leisure to re-examine into the 

 question. 



In September, 18S3, I exchanged 

 also a few letters with Mr. Britton 

 concerning pollen-tubes. On that oc- 

 casion he mentioned also the fortui- 

 tous experience he met with in Cy- 

 pripedium acaiile^ the same as he 

 mentioned in his paper ; by not allud- 

 ing to any other observation of his 

 own in support of his criticism, one 

 might be induced to draw the infer- 

 ence that with this casual and super- 

 ficial observation in the field, his re- 

 searches after pollen-tubes have been 

 exhausted. 



I have also observed more than 

 once bundles of fibres like a skein of 

 silk filling the style, of which Mr. 

 Britton speaks ; but the idea never 

 occurred to me that they were pollen- 

 tubes. I took them for a bundle of 

 fibrillas of the conducting tissue, 

 which, in the wall of the ovary, run 

 down in the rear of the placenta and 

 in close proximity of the ovules. I 

 have prepared a slide showing this 

 very plainly. The material is from 

 an Orchis. 



The slide of jSlonotrapa 71 ni flora ^ 

 which, at the same meeting of the 

 New York Microscopical Societ}', 

 became the subject of a magic-lan- 

 tern exhibition, was kindly loaned to 

 me by Mr. Joseph Schrenk al^o in 

 1S83. On returning it I took occa- 

 sion to mention that the fibre seen to 

 appi^oach the micropyle of one of 

 the three or four ovules the slide con- 

 tains, was not a pollen-tube, accord- 

 ing to my conception, but a branched 

 fibre of the conducting tissue, and my 

 more recent investigation in Alono- 

 trapa would not allow me to change 

 my opinion in this respect. 



Angiospermous plants with ortho- 

 tropous ovules would offer the greatest 

 facility to fecundation by means of 

 pollen-tubes, but these are only of 

 limited occurrence ; plants, on the 

 contrary, having anotropous ovules 

 comprise the largest number, and 

 these would offer also the "-reatest 



