OK

https://ja.wikipedia.org/wiki/ジャボチカバ
https://ja.wikipedia.org/wiki/植物の進化
https://en.wikipedia.org/wiki/Microphylls_and_megaphylls

I looked some more into it, 小葉 has "small leaf" meaning on daijisen/daijiten/daijirin, so that should also be relevant I think (although currently missing on JMDict)
Also in the first reference link above from wikipedia they are used with 系: 日本では小葉系と大葉系と中葉系（大実の成る系統はアッスーと名付けられている）に分類され流通している。

From the second link: 一般的には葉と言えば「大葉（en:megaphylls）」であり and 大葉（いわゆる「葉」）の葉脈の枝分かれパターンは、2分岐が網目状になったものが起源である可能性がある。
So it seems to be more about the fact that 大葉(Megaphylls) have a complex network of veins, as it explains in the third link
So the j-j dictionary entries might be not up to date on this

@@ -19,0 +20 @@
+<gloss>megaphylls</gloss>

大辞泉 seems to be alone with that sense.

Funny that no other reference has it. WWW hits and images are all for perilla leaves.

@@ -13 +13,3 @@
-<gloss>large leaf</gloss>
+<xref type="see" seq="1311720">紫蘇</xref>
+<gloss>beefsteak plant</gloss>
+<gloss>perilla</gloss>
@@ -18,3 +20 @@
-<xref type="see" seq="1311720">紫蘇</xref>
-<gloss>beefsteak plant</gloss>
-<gloss>perilla</gloss>
+<gloss g_type="lit">large leaf</gloss>

https://kotobank.jp/word/大葉-450531

missing definition for "大きな葉。"

@@ -9,0 +10,5 @@
+<sense>
+<pos>&n;</pos>
+<pos>&adj-no;</pos>
+<gloss>large leaf</gloss>
+</sense>

Entry created