ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 227 



Biological peculiarity of AzoUa caroliniana.* — M. Westermaier 

 and H. Ambronn have observed that this species presents the pecu- 

 liarity of throwing off the root-cap from older roots, a great number 

 of hairs being also formed at the apex. An organ is thus produced 

 which resembles the submerged leaf of Salvinia in both form and 

 function. A structure which is neither normal leaf nor normal root 

 is formed, in Azolla by the metamorphosis of a true root, in Salvinia 

 by the abnormal development of an organ which originates as a 

 normal leaf. These root-hairs of Azolla caroliniana are produced in 

 moderately regular transverse rows, each proceeding from a segment 

 of the triangular-pyramidal apical cell. This tendency reaches at 

 length the apical cell and youngest segments, and causes the root-cap 

 to be thrown off. 



Muscineae. 



Female Receptacle of the Jungermaniiiese Geocalycese-t — 

 Leitgeb has established the general rule that the female receptacle of 

 the Jungermannieje always originates in the apex of the shoot, and 

 that wherever archegonia are found on older parts of the stem, they 

 are always products of a lateral shoot. This rule applies to all 

 Hepaticse ; there is only this point of difference, whether or not the 

 apical cell is completely absorbed in the formation of the archegonia. 

 In the former case the receptacle then actually occupies the apex of 

 the axis, which it does not appear to do in the latter case. These 

 two modes of life of the Hepaticee he terms acrogynous and anacro- 

 gynous. No exception was found to this rule in a very large number 

 of species examined. In all cases the origin of the archegonia at 

 spots distant from the apex of the stem can be traced back to an inter- 

 calary lateral shoot. To this case belong the archegonia which spring 

 from the ventral side of the stem in Calypogeia, Geocalyx, and Sarco- 

 gyne. But in the family of Geocalyceae there are some genera in 

 which the archegonial receptacles have not a ventral insertion, but 

 either stand at the apex of a shoot, or the mouth of the fertile tube lies 

 on the dorsal side of the stem. 



The most remarkable peculiarities are presented by Gongylanthus 

 ericetorum, from Madeira, where all the archegonial receptacles are 

 seated in a fork of the stem, forming also the close of an axis, the 

 apical cell of which is used up in this formation. In contrast to the 

 rest of the European Geocalyceso, the archegonial receptacles are in 

 this species produced at the apex of normally leafy aerial shoots. 

 They are always preceded by the production of lateral branches, the 

 rapid and early development of which causes their insertion to 

 coalesce completely with the imbedded receptacle, which projects as a 

 protuberance on the ventral side. The consequence of this is that the 

 receptacle is completely pressed aside from the margin of the fork to 

 the dorsal side of the shoot. This displacement must not be regarded 

 as a phenomenon which takes place only on the reproductive shoots ; 

 it is a necessary result of the earlier development of the lateral shoot, 



* Abhandl. Bot. Ver. Prov. Brandenburg, xxii. (1880) pp. 58-61 (1 pi.). See 

 Bot. Zts?., xxxix. (1881) p. 580. 



t SB. K. Akad. Wiss. Wien, Isxxiii. (1881). 



Q 2 



