1882.] 



MICROSCOPICAL JOURNAL. 



105 



plants he describes in my cabinet ; 

 his descriptions are correct, but I 

 failed to detect any pollen-tubes on 

 their way to the foramen. 



I am at a loss to account for my 

 inability, after having dissected hun- 

 dreds of ovaries in various stages of 

 development, to observe in a single 

 instance the entrance of a pollen- 

 tube into the micropyle ; for some 

 time I attributed it to a want of skill 

 in preparing my sections, but since I 

 have had an opportunity to compare 

 my preparations with some which, it 

 is said, Hofmeister used as a basis 

 for his descriptions, I came to the 

 conclusion that this was not the 

 cause : it must be sought for some- 

 where else. At all events, it seems that 

 the entrance of the pollen-tube into 

 the foramen has been only observed 

 in a few plants. Schacht, in his 

 works, mentions : Carina, Viscum, 

 Najas, Passiflora, and some gerania- 

 ceae. I have examined these plants. 

 In most of them the tubular appen- 

 dices of the pollen-grains on the 

 stigma are easily observable, but 

 very soon they appear to discharge 

 their contents in the conducting tis- 

 sues of the style, and lose their ex- 

 istence as tubes. 



My observations on cactaceae led 

 me to believe that here I might meet 

 with success, but I was disappointed 

 again. I made a phyllocactus, com- 

 monly called "crab cactus," the sub- 

 ject of particular study, and as a re- 

 sult of my observations, I venture the 

 following statement : 



The pollen-tubes insinuate them- 

 selves amongst the papillae of the 

 stigma where, on bursting, the fovilla 

 is taken up by the conducting tissue 

 of the style. This tissue is composed 

 of very fine fibrillse, full of granular 

 matter, whilst the process of fertiliz- 

 ation is going on. At the base of 

 the style, it spreads itself out over 

 the walls of the ovary ; it accom- 

 panies the vascular bundles in the 

 funiculii from the placenta, up to 

 their juncture with the ovules. The 

 tuft of papillae surrounding the mi- 



cropyle of the anatropous ovule 

 meets near the placenta the tuft of 

 the conducting tissue of the funicu- 

 lus, where the papillae of the former 

 absorbs, by endosmosis, the granular 

 contents of the latter, and in this way 

 I conceive that fertilization takes 

 place. 



In the closed flower-bud of the 

 same species of cactus, the stigma, as 

 a matter of course, is yet free from 

 pollen-grains and their appendices, 

 but the conducting tissue is present 

 in the style ; it contains already a 

 number of granules, different how- 

 ever from the granular matter present 

 in the conducting tissue during the 

 process of fertilization. 



The observations on " crab cactus " 

 furnished me the data for a nev/ 

 theory of fertilization, and Cereus 

 grandiflora (night-blooming cereus) 

 furnishes data to arithmetically de- 

 monstrate the impossibility of fertili- 

 zation of the vegetable ovules tak- 

 ing place, in the cactaceae at least, 

 according to the old one. 



The specimen under investigation, 

 gave the following data : — 



Length of style, 9 inches (a hollow 

 tube ^-inch in diameter). 



Ovarian cavity, a cylinder -^-inch 

 in diameter, and over one inch 

 in height. 



I made about forty transverse sec- 

 tions of the ovary, sufficiently thin to 

 count 100 to the inch. Each section 

 contained about thirty ovules, of which 

 the greater number, however, floated 

 off the knife, the funicules having 

 been cut ; the number of ovules in 

 the ovary, would thus amount to at 

 least 3,000. 



The style, in transverse sections, 

 shows a ring of eighteen vascular bun- 

 dles corresponding to the eighteen di- 

 visions of the stigma. Inside this ring 

 is contained the conducting tissue, 

 forming a hollow tube, the nature and 

 compactness of which precludes the 

 possibility of giving passage to 3,000 

 pollen-tubes. In the ovarian cavity 

 there is also no room for 3,000 pollen- 

 tubes, after they should have descend- 



