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



For a time the further growth of the pollen tube toward the 

 female gametophyte proceeds very slowly, so that four weeks later 

 it has penetrated scarcely more than a third of the distance from 

 the tip of the nucellus to the embryo sac. Simultaneously with 

 the appearance of the archegonium initials in the female pro- 

 thallium, however, the pollen tube commences to force its way 

 rapidly through the nucellar tissue, crushing and disorganizing the 

 cells of the nncellus with which it comes in contact, and in a few 

 days enters the archegonial Chamber where its tip presses iip close 

 to the archegonium complex (fig. 91). Lawson (1907 b) states that 

 in the Cupresseae the contents of the yarious tubes are discharged 

 into a common archegonial Chamber. While this may be true in 

 some cases for J. communis, repeated observations of instances 

 where more than one pollen tube have entered the archegonial 

 Chamber show that as a rule the male elements continue to be 

 enclosed in their respective tubes until the discharge of the male 

 cells into the egg. Throughout the period which has just been 

 described the body cell and the two vegetative nuclei are found 

 close together near the lower end of the tube (figs. 48 — 51). 

 The stalk and tube nuclei enlarge somewhat and become so nearly 

 alike that it is impossible to distinguish one from the other, while 

 the body cell increases enormously in size and, just previous to 

 the formation of the male cells, attains a diameter of about 60 ju. 



The presence of a distinct delimiting membrane about the 

 body cell in gymnosperms was apparently first noted by Hof- 

 meister (1851) in Juniperus sibirica. It has since been described 

 in J. communis by Belajeff (1893), Noren (1904, 1907), and 

 Sludsky (1905), and appears to be a characteristic feature in all 

 the Cupresseae thus far studied. A similar structure is found 

 among the Taxeae, and in Sequoia. Among the Podocarpeae, on 

 the other band, a membrane is present about the young body cell 

 of Dacrydium (Young 1907), but soon disappears, while such a 

 structure is apparently entirely absent mPodocarpus (Coker 1902), 

 Saxegothaea (Noren 1908), and Phyllocladus (Kildahl 1898). 

 Among the Äbieteae the body nucleus is surrounded only by a 

 dense zone of cytoplasm which may include also the stalk and 

 tube nuclei. In the cycads and Gingko a membrane is always 

 present. 



The demonstration of blepharoplasts in the body cells of the 

 Gingkoales and Cycadales suggested the possibility that some traces 

 of cilia-forming organs might exist among the Coniferales and 

 Gnetales. A careful study, however, of a large number of body 

 cells in J. communis depressa, in all stages of development, has 

 failed to reveal any structures which appear to be definitely homo- 

 logous with blepharoplasts. As in the other Cupresseae, the body 

 cell is densely packed with starch. A radiate structure of the 

 cytoplasm has been described by Coker (1903 b) in Taxodium, 

 and by Noren (1907) in J. communis, but has not been observed 

 by the writer. 



