Nichols, A morphological study of Juniperus communis var. depressa. 215 



The division of the body cell. — The division of the 

 body cell to form the male cells takes place about four days after 

 the pollen tube enters the archegonium Chamber, and less than 

 three days before fertilization. As pointed out by Coker (1903b) 

 in Taxodium, this division usually occurs almost sinmltaneously 

 with that of the central cell of the archegonium. Ordinarily two 

 male cells, equal or nearly so in volume, and bounded by definite 

 membranes, are formed, as described in the European form by 

 various observers. These cells are at first hemispherical and lie 

 close together (figs. 58, 52, 91), but after separating they become 

 approximately spherical (figs. 53, 94). A slight inequality in their 

 size is sometimes noticeable, but there is no doubt that they are 

 physiologically equivalent, as will be proven later. The formation 

 of two functionally equivalent male cells is of uniform occurrence 

 among the Oupresseae and in Sequoia. On the other hand, but 

 one male cell (or nucleus) appears to be functional in the Taxeae, 

 Podocarpeae, and Abieteae. It would seem, as suggested by Juel 

 (1904) and Coker (1907), that the formation of two functionally 

 equivalent male cells (or nuclei) is restricted to those genera in 

 which one pollen tube comes in contact with, and therefore has 

 the opportunity to fertilize, more than one archegonium. 



Juel (1904) describes in Ou/pressus Qoweniana a pecuüar 

 condition which has occasioned considerable discussion. Here he 

 finds that, in contrast to the usual conditions among the Oupresseae, 

 several (as many as twenty) male cells are formed in a Single 

 pollen tube. Lawson (1907b) examined two other species of 

 Cupressus and finds that there more than two male cells are 

 never produced. He therefore regards the condition observed by 

 Juel as "simply an interesting abnormality". Juel, however, 

 considers this phenomenon a reversion to a primitive type and, 

 coupling it with the fact referred to above that in this group it 

 is possible for a Single pollen tube to fertilize several archegonia, 

 he concludes that the phylogeny of the Oupresseae has been 

 different from that of the other conifers. Juel's opinion that the 

 Oupresseae are descended from an ancestor in which a complex 

 of male cells was formed is strengthened by the results of Cald- 

 well (1907), who finds that in Microcycas such a condition actually 

 exists, and that there the male gametophyte normally develops 

 sixteen male cells. Moreover Noren (1907) describes the occurrence 

 in the pollen tube of J. communis of a large body cell with three 

 nuclei, while the writer has noted several cases in the form under 

 consideration where more than two male cells have been 

 formed by the division of the body cell. Fig. 54 represents 

 an instance where four male cells have been thus produced. To 

 be sure, such conditions are not normal, and it is probable that 

 two of these cells always develop at the expense of the others, 

 so that eventually only two are functional, as might be inferred 

 from the conditions shown in flg. 94. But although the writer is 

 not prepared to discuss the question of the probable ancestry of 

 the Oupresseae, he ventures the opinion that the unusual conditions 



