ON THE HIGHER CRYPTOGAMOUS PLANTS. 117 



The next paper on the subject was an essay published by Dr. Mettenius* 

 in 1846, in which the anatomy and development of /ya^umfa is treated at 

 length; that o{ Pilularia and Marsilea less perfectly. He did not observe 

 the process of impregnation described by Schleiden, yet from the want of 

 organic continuity between the embryo and the " ovule," he inclined to adopt 

 the theory of fertilization propounded by Schleiden, both for the Phaneroga- 

 mia and the Rhizocarpeae, namely, that the end of the pollen-tube penetrated 

 into the so-called ovule and became the embryo ; nevertheless he had some 

 doubts, since he could not reconcile the production of " pollen-tubes " from 

 the small spores of Salvin'ia with the facts he had observed, and never saw 

 the " tube" penetrate the " ovule " in Pilularia. 



In 1846 Prof. Nageli published some new and important observations on 

 Pilulariaf, in which he stated that the observations of Schleiden were alto- 

 gether incorrect, and that the bodies which that author had described as 

 three or four " pollen-tubes," produced by the small spores and adherent to 

 the summit of the large spore, were in fact parts of this, constituting a papil- 

 liform structure, forming a part of the pro-embryo developed by the large 

 spore itself. Moreover he discovered a totally unexpected fact in regard to 

 the small spore or " pollen-grains." He found that these, without coming in 

 contact with the large spores at all, became elongated by the inner coat pro- 

 truding like a short pouch-like process through the outer. This contained 

 starch-granules; and s<ome he found burst and surrounded by starch-grains 

 exactly like those inside the others ; and in addition to these, minute cellules 

 which seem to have been expelled from the small spores. In these cellules 

 were developed spiral filaments exhibiting active movement, just like those 

 of Chara, the Mosses, &c. These filaments finally make their way out and 

 swim about freely in the water. They were constantly met with in the gela- 

 tinous mass in which the spores were enveloped. 



In 1849 M. Hofmeister J published the essay on the higher Cryptogams 

 already alluded to, and there briefly described his own critical observations, 

 referring to the points of difference from his predecessors. His statements 

 are as follows : — 



" The publications of Mettenius and Nageli, as also those of Schleiden 

 himself, sufficiently show that the large spores of the Rhizocarpeae (the organs 

 called by Schleiden 'seed-buds' (ovules)) originate essentially in the same 

 way as the spores of the Cryptogamia generally, and as the small spores of 

 the Rhizocarpeae ('pollen-grains' of Schleiden) in particular. One young 

 spore in each sporangium becomes developed more rapidly than the others, 

 and finally usurps the whole cavity. At the time when the spores are ripe, 

 a large spore does not differ from a small one in any respect except in dimen- 

 sions (the size of the organs allows of the structure of the outer secreted 

 layer being very distinctly observed ; An Pilularia five layers can be clearly 

 detected). The large spore is a simple tough-walled cell filled with starch 

 or oil-drops and albuminous matter, enclosed by a thick exine, which, at the 

 point when the ' sister-spores' were in contact with the developed spore in 

 the earlier stages, exhibits peculiar conditions of form, displaying, according 

 to the generic differences, a splitting into thin lobes or a considerable thin- 

 ning of the mass. Not the least trace of the cellular body (the pro-embryo, 

 papilla of the nucleus of Schleiden) is to be seen at this point at the time when 

 the spores are just ripe. 



* Beitrage zur Kenutniss der Rhizocarpeae. Frankfort, 1846. 



t Zeitschrift ftir Wiss. Botanik. Heft 3, 4. 188, 1846. 



t Botanische Zeitung, vol. vii. 1849 ; Botanical Gazette, vol. ii. 1850. 



