ZOOLOGY AND BOTANY, MICROSCOPY, ET< '. 605 



formation of the simpler type seems often to be associated with limitation 

 of growth, the entire growing-point being given over to the production 

 of gemmae. The production of discoid gemmae, on the other hand, rarely 

 seems to affect the growth of the plant much. Gemmae of the simple 

 type are much common on northern forms, whereas discoid gemmae occur 

 chiefly on tropical epiphyllous species. In New England two species 

 bear discoid papillae, namely, Gololejeunea Biddlecomise and Radula com- 

 planata, and it is the development and structure of the gemmae in these 

 that is discussed by Stevens. 



Protonema and Propagules in Hepaticae.* — I. Douin treats of the 

 protonema and propagules of the hepaticae. A 2-celled propagule of 

 Leioscyphus anomalus gives rise to a prothallus of four cells, then to a 

 rudimentary thallus, the two together constituting the protonema of the 

 species. A rude stem with rudimentary leaves then arises, and, finally, a 

 normal stem, leaves, and small amphigastria. A similar course of events 

 is seen in the case of the germinating spores of G&phaloziella striatula. 

 Thus in their development is found a link between the foliose and the 

 thalloid Jungermanniaceae, just as there is a link in their mode of fruc- 

 tification. Moreover, the importance of the propagules is seen in the fact 

 that they transmit the same qualities as the spores, giving rise to the 

 same course of development, and, though much neglected, they have a 

 systematic value, if wisely used. They are produced with special pre- 

 cautions by the plant. For example, to protect them, amphigastria are 

 developed in several species of G&phaloziella and Cephalozia, in which 

 ordinarily no amphigastria are found. The propagules, in case of 

 dioicous plants, carry on the sex of the parent plant, just as the spores 

 do — at least, they behave just as true cuttings would. Thus Gepha- 

 loziella dentata is sterile in Eure-et-Loire, and reproduces itself entirely 

 by propagules ; the plants, indeed, produce archegonia annually, but 

 never have tliem fertilized, owing to the absence of the male element. 

 Propagula do not vary much. They are multicellular and lenticular in 

 Marchantia, Lunularia, Blasia, and Radula. But more commonly they 

 are 2-celled and elliptic or angulate, as in Cephalozia, Lophozia, Mar- 

 supella, Amur a. They are unicellular in Galypogeia. And in Gongy- 

 lanthus they were once seen to be in tetrads. 



Rhizoids of Marchantiales.t — V. Schiffner discusses the rhizoids 

 of Marchantiales. These are of two kinds : (1) the smooth-walled ; 

 (2) those with internal papillae (Zapfchenrhizoide). The latter are 

 peculiar to the Marchantiales and do not occur at all in the Junger- 

 manniales and Anthocerotales. Their meaning has been variously 

 explained, but not in a manner to satisfy Schiffner. Botanists of the 

 present day are, he says, too ready to invent biological meanings for 

 every plant structure. He gives a resume of the suggestions made by 

 Strasburger, Leitgeb, Kny, Haberlandt, Stephani, Kamerling, Goebel. 

 Schiffner himself, after examining a vast number of specimens, has 

 come to the conclusion that the papillate rhizoids do at times conduct 

 water as a part of their functions, and that the papillae do prevent the 



* Rev. Bryolog., xxxvii. (1910) pp. 73-7 (figs.). 



t Ann. Jard. Bou. Buitenzorg, 3e Supp. (1910) pp. 473-92 (figs.). 



