Oliver . — The Ovztles of the older Gy mno sperms. 463 
whilst in the canopy we seem to have a structure whose 
homology, like its function, is at present obscure. It would 
be premature to enter into any discussion as to the relations of 
this seed until its structure has been more fully elucidated. 
3. Cycads. 
The ovule in this group offers so general an agreement with 
the usual palaeozoic type that any view of its affinities seems 
inadmissible which excludes relationship with the Radio- 
spermeae and Platyspermeae. The main difference is found 
in the fact that only at the apex are nucellus and integument 
free from one another. 
The pollen on its entry into the pollen-chamber becomes 
rooted by haustorial attachments in the wall of the chamber. 
It thus obtains adequate nourishment for its further develop- 
ment. In due course the pollen-grain extremities of these 
tubes undergo a stretching, so that the sperm-cells are brought 
down close to the necks of the archegonia. Here they are 
liberated, the necessary fluid for their swimming being sup- 
plied, in some cases at any rate, from the tubes as they 
burst k 
The distribution of the vascular system in the Cycadean 
ovule demands some consideration. Though the general 
plan is fundamentally the same throughout the group, there 
is considerable variation in detail in the different genera and 
even species. The case here set forth is that of Cycas 
Rumphii 2 (Figs. 4-8). The common supply-bundle gives 
off the branches to the integument before its actual entry 
into the ovule (Fig. 4 sb.), and then continues its course into 
the chalaza ( cb .). The integumental bundles are two in 
number and run in the sarcotesta undivided to the micropyle. 
The plane in which they run is known as the principal plane 
of the ovule. Before these integumental bundles pass beyond 
the chalazal region, however, each gives off an internal 
1 H. J. Webber, Spermatogenesis and fecundation of Zamia, 1901. 
3 I have to acknowledge much assistance from Miss Edith Chick, in the study 
of the structure of Cycadean ovules. 
