igo 



BOTANICAL GAZETTE [September 



A complex of male 



Cup 



DACRYDIUM 



material 



Professor 



.r.t 



I 



Chamberlain (5), who suggests that the complex is prothallial and 



the two nuclei reproductive. 



In 1904 JuEL (6) found in the pollen tubes of Cupressus Goveni- 



ana a complex of male cells; sometimes there were only four, but 

 more often eight or ten, and in one case about twenty. The tree 

 was grown in a greenhouse and may not have been normal. Recently, 

 however, a study of Microcycas calocoma by Caldavell (7) has 

 revealed a somewhat similar multiplication of reproductive cells. 

 He found in the pollen tube a tube nucleus, a prothallial cell, a stalk 

 cell, and eight or nine body cells. Each of these body cells later 

 divides to form two sperm mother cells. 



The peculiarity of the pollen grains of Podo carpus and its possible I 



bearing on the question of relationships among conifers added con- 

 siderable interest to the study of Dacrydium. A brief summary of 

 some points in our present knowledge of the male gametophytes of 

 conifers may be useful. 



1. Prothallial cells. — Taxineae, Taxodineae, and Cupressincae 

 have none. In Abietineae there are two and both are ephemeral. 

 In Podocarpus there are originally two; one at least is persistent and 

 may divide. In Araucaria, as Chamberlain interprets Lopriore^s 

 figures, there is extensive prothallial tissue. 



2. Generative cells. — The free nucleus of the spore divides to form 

 lucrative cell and tube nucleus. Usually the generative cell 



divides periclinally to form the so-called stalk and body cells, of which 

 the former is sterile. 



3. The male cells. — The body cell divides to form two male cells 

 or nuclei. The sperms are usually unequal, but in Taxodium and 

 Juniperus, and perhaps in Pinus, they are equal. 



4. Shedding. — The usual shedding-stage is after the division into 

 tube nucleus and generative cell; but in Juniperus and Cupressus 

 the microspores are shed before any division has taken place ; and in I 



Picea the generative cell has divided. ' 



J 



