ON THE STKtJCTUKE AND AFFINITIES OF CHARACEiE. 205 



gamic termiiiology, arising in great measm-e from the unfortunate 

 use of the corresponding term ''Voriceim" by Pringsheim and 

 other German writers. Both etjanologically, and by homology with 

 the pro-embryo or "suspensor" of Gymnosperms and Angiosperms, 

 the use of the term should be confined to a structure intermediate 

 between the act of impregnation and the formation of the multi- 

 cellular embryo, such as appears to occur in SelaginellecE alone 

 among flowerless j)lants. The so-called pro-embryo " (Vorkeim), 

 on the contrary, of Mosses and Chara is a structure proceeding 

 immediately from the spore, and anterior to the formation of 

 the sexual organs. It is strictly homologous with the pro- 

 thallium of Vascular Cryptogams ; the difference being only 

 of secondary importance that in the latter the prothallium 

 produces immediately the archegonia and antheridia, while in 

 MuscinecB the leafy x^lant intervenes. If, however, the term prothallium 

 is open to objection, there is none to the retention of protonema. 

 A false analogy has even led some otherwise careful writers into 

 the error of speaking of the " pro-embryo " and the leafy plant of 

 Chara as exhibiting the two stages of an alternation of generations.! 

 The phrase "alternation of generations" is, in fact, used with 

 great vagueness by many cryptogamists. If we employ the term 

 in its best accepted sense, as exhibited in Vascular Cryptogams, it 

 simply describes the fact that the life-history of many plants can 

 be divided into two distinct stages, separated by definite starting- 

 points ( Wendungsi3unkte) ; these two points being the act of 

 impregnation of the female by the male element, and the germina- 

 tion in the soil of the spore produced non-sexually. The sexual 

 generation consists of the stage intermediate between germination 

 and impregnation ; the non- sexual generation of the stage inter- 

 mediate between impregnation and germination. In this sense, 

 the " pro-embryo " of Chara and the protonema of Mosses are 

 both a part only of the sexual generation,! although even Sachs 

 often speaks vaguely .of the protonema of Mosses "intervening" 

 between the spore and the sexual generation. In both Characea 

 and Mosses, the remainder of the sexual generation, or leafy plant, 

 is produced on the protonema by lateral budding. The confusion 

 to which I have just referred is no doubt increased by the extra- 

 ordinary want of exactness in the use of the word "spore" by 

 even some of the best writers on cryptogamic botany, — a practice 

 which has thrown great confusion over many points of cryptogamic 

 homology, and to which it is of the highest importance to attempt 

 to put an end. Even Huxley and Martin § (' Course of Practical 

 Instruction in Elementary Biology,' 4th edition, 1877) describe 



* I must confess to having myself sanctioned the confusion by .my rendei'ing 

 of Vorkeim by "pro-embryo " in relation to Cryptogams in the translations both 

 of Sachs's and of Thome's ' Lehrbuch.' 



+ Kepeated by myself in my edition of Thome's ' Lehrbuch.' 



J This view |is confirmed by the fact that in Chara fragilis branches are 

 produced from the nodes of the stem — called by Pringsheim '• pro-embryonic 

 branches " (Zweigvork^ime) — altogether similar to the so-called " pro-embryo," 



§ The same terminology is perpetuated in the 3rd edition (just published) of 

 Henfrey's 'Elementary Course of Botany.' 



