1856.] The Qryptogamia. 315 



commonly be wanting in the ordinary kind of seeds, for the reproduction 

 of the species. But this want is supplied by what are called sporules ; 

 bodies which, in their physical construction, are nearly the same as the 

 pollen of flowering plants, and in general appearance very much resem- 

 ble the seeds of those plants, except that the pericarp is wanting — hence 

 the tissue is left naked. We also remark another fact peculiar to the 

 plants of this order alone, which is, that they are entirely composed of 

 cellular tissue, from the root to the leaf, if we may call the expansions 

 which we often see on them, leaves, although they do not answer the pur- 

 pose that the leaf usually does. In order to prevent confusion, it becomes 

 absolutely necessary to have a systematic arrangement of all plants 

 coming under this head ; thus we may pass easily from one genus to 

 another, and from species to species, noticing all resemblances and dis- 

 similarities, with entire satisfaction, and perfect clearness: consequently, 

 this order has lirst been divided into two great classes, called Acrogens, and 

 Thallogens ; evidently so called from the manuer of their growth. Thus, 

 the name of the former implies, that they grow on the end or point, while 

 not increasing in diameter ; while the latter grow into an expansion, 

 called the thalius. The acrogens include all those plants which in their 

 structure approximate to the phaeuogamia ; and the thallogens, quite an 

 interesting class, is composed of plants of the very lowest species of the 

 whole vegetable kingdom. 



Under the head of acrogens, let us first notice the ferns : these plants are 

 provided with fronds, or expansions, very similar to leaves in shape and 

 color, but designed for an entirely different use ; arising from the axis 

 of the plant, like a stem, they bear sporules which are developed upon 

 the external surface. We, in this country, are not so well acquainted 

 with the beauty of these plants, as those who dwell in parts where they 

 grow abundantly, as in the tropical regions. Gray remarks, in regard 

 to this subject, that " although the ferns of the United States, and of all 

 northern climates, have prostrate stems, and consequently do not rise 

 more than three or fuur feet in hight ; yet in tropical countries their 

 trunks are often erect, and frequently attain to ihe hight of seventy oi 

 eighty feet. The tree-ferns of the tropics are said to be objects of incom- 

 parable beauty ; their straight, unbranched trunks, often rising, like 

 those of palms, as high as foity or fifty feet without a leaf." But, let 

 us hasten to notice the mosses v/hich adorn the rugged trunks of our 

 forest trees, and give a velvet coating to the dull weather-beaten rocks, 

 to which they are attached by delicate, brown roots. These bear often 

 a little urn, with an interesting cap upon it; and this urn contains 

 those sporules, which in the ferns were produced upon the inferior 



