626 



Having lately seen the articles on this subject by Schleiden, and 

 by Mirbel and Spach, in the * Annales des Sciences Naturelles,' pub- 

 lished in April and May, 1839, it has been my wish to examine for 

 myself how far the former of these writers had any foundation for his 

 opinions. Hitherto I have not met with any evidence in favour of the 

 doctrine which teaches that the vegetable embryo consists of a por- 

 tion of the pollen-tube which has penetrated the nucleus. The ac- 

 count given by Corda (see Lindley's ' Introduction,' ed. 2, p. 550) may 

 possibly be correct as applied to the spruce fir, which I have not yet 

 examined, but it can scarcely be applicable to Pinus sylvestris, where 

 I find the nucleus surrounded by three different integuments, each of 

 them destitute of a foramen ; so that all direct communication of the 

 pollen-tube with the nucleus appears to be impossible : it would even 

 admit of a doubt whether the ovule in this case is really naked, and 

 whether there be not a carpellary membrane (continuous with the 

 stigma-like expansion at the summit of the ovule) surrounding the 

 nucleus and its proper integuments. The innermost of the three 

 membranes is a very thin pellicle [sac of the embri/o of Adolphe Brong- 

 niart), scarcely if at all attached to the surrounding parts. A lon- 

 gitudinal section of the ovule is given at fig. 2 (p. 625). The action 

 of the pollen has not yet been observed. 



A genuine example of a naked ovule may be seen in Juniperus 

 communis. Here the nucleus consists of a roundish mass of uniform 

 cellular tissue, not enclosed in a pellicle, and with only one integu- 

 ment, which is open at the top ; so that there is nothing to prevent 

 the pollen-tube from penetrating the nucleus. It must, however, be 

 remarked, that the nucleus has no ready-formed cavity {embryostome) 

 for the reception of the pollen-tube, and thus far the observations of 

 Corda seem to be inapplicable. The like structure exists in Thuja 

 occidentalis. Unfortunately, I cannot pursue the enquiry; as the 

 male plants of both are inaccessible to me at this time. Fig. 3 (p. 625) 

 represents a longitudinal section of the ovule of Juniperus ; at fig. 4 

 is shown another actual section (exceedingly thin) of the nucleus, 

 with a portion of the integument, carefully copied from nature, mag- 

 nified about 300 times. 



In Berberis vulgaris there are some interesting features. The ova- 

 rium is a cavity, imperfectly closed at the top by the stigma. There 

 is no proper style, and no central stigmatic tissue ; so that if any pol- 

 len-tubes are formed, they must pass at once into the ovarium, and 

 into the foramen of the ovule : but it is not yet ascertained that any 



