80 SUMMARY OF CURRENT RESEARCHES RELATING TO 



ever, contiDgent upon a stimulus following fertilization. Therefore, the 

 perichaetia find no analogue in the antheridial inflorescence. Their 

 occurrence is limited to the thallose forms. In these the perianth may be 

 absent, as also in a number of Marchantiacese with small sporogonia 

 protected by the perichaetium, and in some Jungermannie^e {Fellia, 

 Blyttia, Symphyogyna) in which the sporogonium buries itself deep in 

 the tissues below the archegonium. The same applies to some acrogjnous 

 forms. Also the subsequent development of the perichgetium can be 

 dependent on fertilization. It is not this dependence, but the compara- 

 tive morphology, which is the criterion for the involucres. 



Sporophyte of the Hepaticse.* — R. Douin gives an account of the 

 sporophyte of the hepatica3, studying the different parts of the sporo- 

 gonium with their principal variations, and the organs developed for 

 their protection, more especially the calyptra ; he also shows the value 

 of the systematic characters drawn from these organs for distinguishing 

 the principal groups. He treats of ; (1) the sporogonium with its foot, 

 pedicel, and capsule : (2) the organs that protect the sporogonium, 

 namely, the calyptra, perianth, involucre, perigynium, and sometimes 

 even the thallus or stem — and these he considers in relation to the 

 sporogones, whether isolated on the one hand or grouped on special re- 

 ceptacles ; and (3) employment of characters derived from the sporo- 

 gonium and its envelopes for purposes of classification. Characters 

 derived from the sporogonium are very stable, and are therefore of prime 

 importance ; but those derived from protective organs such as calyptra, 

 perianth, etc. are of somewhat less importance, while those derived from 

 the gametophyte are of much less value, being liable to vary under the 

 influence of external conditions. The hepatics would be much more 

 naturally grouped, if divided according to the development of the sporo- 

 gonium into the three groups — Ricciales, Anthocerotales and the rest of 

 the order, than if divided into Marchantiales, Jungermanniales, Antho- 

 cerotales, where gametophyte characters are largely employed. Among 

 the anacrogynous Jungermanniales two groups appear particularly 

 natural — Sph^erocarpoidese, which should be placed elsewhere, and Metz- 

 gerioideae. The Anacrogynaj form in fact the most artificial of all the 

 groups. The Acrogynae form quite a natural group, but have been very 

 artificially sub-divided into tribes. The classification of the hepatics is 

 far from perfect. Some of the groups are natural enough ; but many 

 others need to be completely revised or replaced. 



Anatomy of Marchantia.f — A. Lamothe writes on the importance 

 of the anatomical characters of the gametophyte of the sub-class Mar- 

 chantiales. The typical creeping dorsiventral thallus consists of : (1) an 

 upper epidermis generally pierced with ostioles ; (2) a stratum contain- 

 ing aeriferous crjpts ; (3) a solid stratum of parenchyma limited below 

 by the lower epidermis bearing rhizoids and scales. A study of two 

 genera of Ricciaceaa and fifteen of Marchantiaceas has led to the follow- 

 ing results. 1. In the Ricciaccae the pseudostomata are simple ; in the 



* Rev. Gen. Bot.,xxiv. (1912) pp. 403-13; 453-63 (4 pis.), 

 t Comptes Rendus, civ. (1912) pp. 1093-6. 



