GAMETOPHYTE 



sion, unaccompanied by a wall, in the outermost cell of the row 

 of three. There is every evidence that in this family the inner 

 cell of the first division always divides, and the other one may 

 or may not divide, resulting in three or four megaspores. 

 Almost the only exception to three or four megaspores, in case 

 the mother-cell divides, noted among Archichlamydeae is Vis- 

 cniii articulatum (Treub 13 ), in which the four or five mother- 

 cells divide only once, the inner cell becoming the functional 

 mega spore./ 



This same variation is found in at least twenty other fam- 

 ilies of the Archichlamydeae. Probably the most variable case 

 recorded is that of Salix glaucophylla (Chamberlain 46 ), in 

 which there may be three megaspores, or two, or the mother-cell 

 may not divide. 



The few cases among Archichlamydeae in which the mother- 

 cells are not known to divide are three genera of Piperaceae 

 (Peperomia, Piper, Heckeria) investigated by Johnson, 79 ' 114 

 but the allied Saururus (Johnson 87 ) has a row of three mega- 

 spores; Alcliemilla alpina (Murbeck 94 ), but this is associated 

 with the occurrence of a large mass of archesporial tissue ; the 

 Cactaceae (D'Hubert 33 ) ; and at least Slum cicutae folium 

 among the Umbelliferae. In Juglans cordiformis Karsten 115 

 finds great variability, the mother-cell functioning directly as the 

 megaspore or giving rise to a row of three or four megaspores, 

 the two outer ones never functioning, the two inner ones appar- 

 ently having an equal chance, and in many cases developing two 

 sacs. Among the Araliaceae also, Ducamp 112 reports that the 

 mother-cell becomes the megaspore directly or produces a row of 

 three or four megaspores. The same is true of the Balanophora- 

 ceae, as shown by Lotsy 82 in Rhopalocnemis, and by Chodat 

 and Bernard 83 in Helosis ; but the conditions in this family are 

 so peculiar that the phenomenon does not seem significant. In 

 Casuarina (Treub 25 ) (Fig. 24) and Quercus (Conrad 78 ), in 

 which there is a large mass of sporogenous cells, there is no 

 division of mother-cells to form spores. The behavior of the 

 numerous mother-cells of Casuarina is remarkable, a certain 

 number developing as embryo-sacs, a larger number remaining 

 sterile and becoming very much elongated, and still others be- 

 coming tracheid-like cells. 



It is apparent, therefore, that among the Archichlamydeae 



