142 Remarks on the 



into the ovary; and Moreland* suggested that the grains even pen- 

 etrate the ovules and become the embryo. The latter author, 

 who was, I believe, the first to extend the hypothesis of Leeu- 

 wenhoek to the vegetable kingdom, inquires ' whether it be not 

 more proper to suppose th 't the seeds which come up in their proper 

 involucra are at first like uniinpregnated ova of animals; that tliis fari- 

 na (pollen) is a congeries of seminal plants, one of which must be con- 

 veyed into every ovum before it can become prolific; that the stylus, in 

 Mr. Ray's language, the n))i)er part of the i)istilluni in Mr. Touriiefort's, 

 is a tube destined to convey these seminal plants into their nest in the 

 ova; that there is so vast a provision made because of the odds there are 

 whether one of so many shall ever find its way into and through so 

 narrow a conveyance.' He then ])roceeds to record several circum- 

 stances, which are, in his opinion, confirmatory of this view; especially 

 the manifestly tul)ular style of the Croum Imperial and some other plants, 

 the cavity of which he erroneously considered to lead directly into the 

 seed-vessel, 'i'his cavity, however, only exists in some com])ound 

 styles, being formed by the cohesion of three or more simple styles, so 

 as to form a hollow cylinder, and it consequently does not conmiunicate 

 with the interior of the ovary. Moreland also observed the micropyle 

 (the vestige of the foramen of the ovule,) in peas and beans; he sup- 

 posed it to be a perforation produced by the entrance of a grain of pollen, 

 which, having fallen down the tube into the ovary, had at length enter- 

 ed the ovule and become the embryo or seminal plant. 



" It was discovered, I think, by Needham, that when grains of 

 pollen are moistened or thrown upon water, they usually burst 

 with violence and discharge the slightly viscous and turbid fluid 

 contained within. To this fluid the immediate agency in impreg- 

 nation was attributed by Linnaeus and contemporary botanists. 

 Two opinions, however, have prevailed respecting the mode of 

 its action upon the ovule; some writers supposing the fluid itself 

 to be conveyed down the style to that organ, while others conceiv- 

 ed that a peculiar action excited upon the stigma was transmitted to the 

 ovule by a kind of sym])athy. The former view appears to have been 

 adopted by Linnaeus. t The latter was sustained by Grew and several suc- 

 ceeding philosophers. Our actual knowledge upon this subject w as, how- 

 ever, confined to the simple fact that the application of the pollen to the 

 stio-ma was essential to the fertilization of the ovules, all the information 

 we possess respecting the action of the pollen after it has reached the stig- 

 ma being of very recent date. The earliest of a series of highly curious dis- 

 coveries on this hitherto mysterious subject was announced in the year 

 1823. A few remarks on the structure of pollen will form a necessary in- 

 troduction to our account of these interesting researches. 



" The pollen, when examined by a moderate magnifying power, is seen to 

 consist of a multitude of grains of some regular form, which is uniform in 

 the same species, but often differing widely in different plants. It has been 

 satisfactorily proved that these grains are composed of two coats, of which 

 the exterior is rather thick and nearly inelastic, while the inner is an ex- 

 ceedingly delicate and highly extensible membrane. The cavity is filled 

 with a fluid, which, under a powerful lens, appears slightly turbid on ac- 

 count of a vast number of minute granules which float in it. The existence 

 of an inner lining to the pollen-grains was ascertained at an early period, 

 first by Needham and afterwards by Koelreuter, and although since 



* "Some nnv Ohsrn^atmis on the Parts and the Use of the flower in plants; by SamuEL 

 Moreland, — Philosophical Transactions, Vol. 23, (1703.)" 



•j- " Generationcm vegetabilium fieri mcdiante poUinis anthcrarum illapsu supra stigmata 

 nuda quo rumpitui- pollen efflatque aurem seminalem, qua; absorbelur ab humore stigmatis, 

 &C.— -Lmn. Phil. Bot. cd Stockholm. 1751. p. 91". 



