\ 
long ago pointed out the true significance of these facts, and 
shown that we have only to continue this same process a step 
beyond what it has already reached in Sa/vinza and Tsoétes to 
arrive at the condition presented by. the existing Gymnosperms, 
the Cycadece@ and Conifere. Here the macrospore exists under 
the name of embryo-sack, while the microspores are the’ pollen- 
grains. The so-called macrosporangia of these highest Crypto- 
gams thus correspond to the ovules! of the Phanerogams, while 
the anther-cells of these latter are homologous with the micro- 
sporangia of the former. The prothallium is readily traced to the 
- Gymnosperms, especially in the fertile flowers, where it re-appears 
under the name endosperm, and constitutes the albumen or reserve 
material of the future seed — one of the finest examples in 
biology of the fundamental identity of the reproductive and 
nutritive functions. In the staminate flowers the prothallium may 
be considered as represented by the pollen-tube (the elongated 
cell that descends from the pollen grains into the ovary and fer- 
tilized the germ), although a careful study of the microspores of 
Tsoétes, in which one cell remains sterile while the rest develop 
the spermatozoa, may leave some doubt as to whether the 
homology is here quite complete. The greatest differentiation 
has gone on in the microspores; the microspores and the plants 
and organs bearing them, still presenting, in many cases, 4 
striking resemblance. In the Cycadacee, for example, the anther- 
cells are sessile and single or in groups upon the lower surface 
of the broad filaments like the “fruit dots” on the back of a 
fern. In the Conifere the stamens are less leaf-like, but the 
pollen-sacks are often solitary and scattered over the under sur- 
face of the flattened filaments. 
An interesting similarity also exists between the male aments 
of certain Taraceæ, as in the yew and the juniper, and the spikes 
of Equisetum, the horse-tail or scouring-rush. In these cases it 
is said that nearly all the morphological homologies are satisfied. 
In general it may be said that in all these respects the Cycada- 
cee resemble most the group of true ferns, the Conifere proper 
(pines, firs, etc.), most the club-moss group (Dichotomes), and the 
1Sachs (Yahrbuch der Botanick, 4 Aufl. S. 481) justly objects to the term ovule (OF 
little egg) as entirely misleading in its etymology, and as tending to perpetuate the 
~ error that gave rise to its use, and proposes the term seed-bud (Samenknospe) a5 4 
substitute. — 
364 On the Genealogy of Plants. | [June, 
ai eh teak Sie ese th a hoe Bir 
