STROBILI 447 
rangia are produced. The name, however, suggests the likeness 
of the microsporophylls to the stamens of Flowering Plants. 
The ovulate strobili are strobili in which only megasporophylls 
and megasporangia occur. The term ovulate suggests the like- 
ness of the megasporangium to the ovule of Flowering Plants. 
The megasporangia are now called ovules because they remain 
closed, so that the female gametophyte is at no time exposed. 
It is obvious that the Cycads have carried the differentiation 
of structures farther than the Selaginellas have. In Cycads, not 
Fic. 397. — Staminate strobilus and microsporophylls in Cycads. At the 
left, a staminate strobilus of a Cycad (Dioon); at the right, microsporo- 
phylls from two different Cycads, showing difference in shape, and the way 
the sporangia are borne. After Chamberlain and Richard. 
only spores, sporangia, and sporophylls are differentiated, but 
there is also a differentiation of strobili. 
The strobili of Cycads are much larger than those of Selaginella 
or Lycopodium, and the sporophylls are usually very different 
from the foliage leaves. In some Cycads the strobili are a foot or 
more in length and several inches in diameter. 
In the staminate strobili, the sporophylls are closely crowded 
and practically have no resemblance to foliage leaves. They 
vary considerably in shape in different Cycads, but have an 
outer, expanded, sterile portion and bear the microsporangia, 
usually grouped in sori, on their under surface (Fig. 397). 
The ovulate strobili are often much larger than the staminate 
strobili. The megasporophylls are usually closely crowded, and 
