INTRODUCTION TO CEYPTOGAMIC BOTANY. 69 



fact, more or less closely, those of Endlicher and Brongniart. 

 The former, then, will be designated as Acrogens, without, 

 however, supposing too strictly that new matter is deposited 

 only at the extremity, and the latter as Thallogens (plants in 

 which there is a fusion of root stems and leaves into one 

 general mass) which is equivalent with that of AmpJiigenoB, 

 of Brongniart. When these two grand divisions are established, 

 we shall be enabled to form a much more clear and precise 

 notion of the objects under consideration. There is no diffi- 

 culty, for instance, in framing some general conception which 

 shall embrace, in the same bird's-eye view, the smallest moss 

 and the most gigantic tree fern, while nothing but a complete 

 ignorance even of the outward characters of the fruit will con- 

 found in the same class, the most frondose Lichen or Alga, 

 with the least frondose Jungermannia. 



5Q. The word Acrogens, as observed before, has been applied 

 to the whole race of Cryptogams. There is no question about 

 its more general application now. Though very insufficient in the 

 first instance, it may be proper enough when used in a restricted 

 sense. In the sequel, I purpose to give such tabular formulae 

 as may assist the student in taking a general view of the subject, 

 and of obtaining some insight into the divisions into which Cryp- 

 togams are naturally divisible, but it will be well, as we proceed, 

 to contrast the prominent distinctions of parallel groups. Crypto- 

 gams,then,in the first instance,are divisible intotwo great groups : 

 f Thallogens. — Seldom herbaceous or provided with foUaceous 

 appendages ; foliaceous appendages, if present, 

 destitute of stomata. Spores rarely producing 

 a prothallus ; and, if so, giving rise to a 

 second order of spores, germinating at definite 

 points. Spermatozoids not spiral.* 

 Acrogens. — Mostly herbaceous, and provided with distinct, 

 often stomatiferous foliaceous appendages. 

 Spores, for the most part, producing a pro- 

 thallus, or if not, complicated fruit by means 

 of the impi'egnation of an embryonic cell. 

 Spermatozoids spiral. f 



* Itzigsohn, however, asserts that spiral Spermatozoids exist in 

 Spirogyra arcta and Gladosporium. Hedwigia, 1852, 1855. 



t It is to be observed that those Thallogens which have the green 



