Catalogue of Works on Gardenmg^ Sfc. S3 



both tribes, although the result is diametrically opposite in each ; the stem in 

 the first being long, and upright or creeping ; in the second globular, simple, 

 branched or many-headed. The genus Pilocereus, which forms the passage from 

 the one tribe to the other, is the only exception. During the first period, in both 

 tribes, the seed swells, the episperm separates from the hilum, and the descending 

 stem issuing from the widening fissure turns towards the earth ; at the same time, 

 the ascending stem rises, carrying up the torn episperm. During the second 

 period, the tribes begin to differ in appearance. The episperm has fallen off, 

 and the ascending stem has become a primordial merithallium ; but, in the 

 Phyllariocotyledoneae, it bears on its summit two ovate and slightly acute 

 cotyledons, while in the Phymatocotyledoneae they are distinctly tuberculate. 

 In both the descending stem becomes the root, and buries itself in the soil 

 preparatory to the emission of radicles. This latter operation seems subject 

 to the evolution of the cotyledons ; for after a short time, in both tribes, these 

 recede from each other, and some very minute radicles appear round the root, 

 and then, opposite to the cotyledons, are seen the two earliest tubercles bearing 

 the rudiments of bundles of prickles, which, evolving themselves opposite and 

 alternately, form at length the future stem. During the third period, the differ- 

 ence between the tribes is striking. In the Phyllariocotyledoneae, the foliaceous 

 cotyledons are obliterated ; the merithallium is nearly buried in the soil, and 

 becomes the true collar ; whilst between the two cotyledons peaks up the cau- 

 licula already indicated by the first two fascicles, and afterwards increased by 

 the spiral evolution of new ones. In the Phymatocotyledonese, on the other 

 hand, the merithallium arises from new tubercles, bearing bundles of prickles, 

 becomes globular from the continuous evolution of others, and finally increases 

 to a caulicula, more or less globose, and always buried. Thus it is easily per- 

 ceived that each tribe has a peculiar and opposite mode of germination." 



Such is the reasoning by which the author supports his theory. To show how 

 he carries it out in practice would take up too much space in a work devoted 

 more to the garden than the study. We must therefore content ourselves 

 with stating that, of his two tribes, the first, or Phyllariocotyledonese, contains 

 six genera ; Peiresck Plum., Opuntia Tourn., Lepismium Pfeiff., Hariota 

 Adans., Epiphyllum Herm., and Cereus C. BauJi. : the second, or Phymato- 

 cotyledoneae, seven ; Echinonyctanthus Lem., Echinocactus L, 4' 0., Mammil- 

 laria Haw., Anhalonium Lem,, Melocactus C. Bank., Pilocereus Lem., and 

 Astrophytum Lem., the place of the last uncertain. 



Mecensio Specierum Generis Pteridk. Auctore Jac. G. Agardh. 8vo, pp. 86. 

 Lund, 1839. 



The object of the work is to rescue the genus Pteris from the confusion 

 into which it had fallen, in consequence of the number of new species added 

 since the revision of Willdenow. For this purpose Dr. Agardh, not content 

 with the Swedish collections, travelled into England, Scotland, France, and 

 Germany, to scrutinise the rich herbariums to be found in those countries. 

 His original design was to publish a monograph of the genus ; but, in the 

 meantime, the appearance of the valuable work of Presl rendered such an 

 undertaking unnecessary, and the doctor contracted his views to a searching 

 examination of the species. Presl had, in the professor's opinion, pushed the 

 use of venation too far in employing it as a generic diagnostic ; and, by so doing, 

 had formed genera which the latter has reunited to Pteris, confining this 

 character to the discrimination of subdivisions of genera only. He divides 

 the genus into four sections, of the value of which the subjoined characters 

 will give an idea. 



1. Eicpteris. Petioles fascicled, greenish or straw-coloured, rarely purplish ; 

 a transverse section of the fascicle of vessels having the shape of a horse- 

 shoe, frequently incurved at the apex. Fronds pinnate; veins parallel, apjjroxi- 

 mate, simple or 1 — 2-forked, rarely anastomosing at the apex or the basal ones 

 forming an arch. Species I — 53. 



2. Ornithopteris. Petioles scattered, green or straw-coloured ; fascicles of 

 Vol. XVI. — No. 118. d 



